This is your compare tray

Apps you want to compare will be listed here. Launch a head to head comparison at any time.

All categories

VoIP.ms

Business Phone and IP telephony system

see alternatives

VoIP.ms Reviews

Reviews summary

Pros

Very easy to set up and manage with good controls on use, coupled with great pricing and a very responsive support staff.

Kris S.

I love the fact that they are really easy to setup and use. I use it more for personal use and absolutely love how I can stay in touch with my family for a fraction of the price.

Paul C.

Very easy to set up - i am using FreePBX. Support has been great - answered my questions and pointed me in the right direction.

mark k.

Cons

No idea how many calls were missed as a result. Call transfer between extension occasionally does not work.

Bernard S.

However, due to the time consuming and lack easy tools to block the spam and junk calls. I am seriously considering moving some of my numbers to Google or other mobile phone service providers.

Ali Y.

The registration of users is not always clear. Sometimes there is a problem, but I don't know all the technical terms to ask about the problem.

Wendy S.

Overall rating

5

4

3

2

1

246

38

9

1

0

97%
positive reviews
99%
would recommend this app

Filter reviews by


Overall rating


Company size


Industry


Time used


294 reviews

recommended

Overall Rating

Best provider I have used

Reviewed 10 months ago

Transcript

Clinton W.: Hi, my name is Clinton and I work in the communications industry, I am a communications director,...

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend9/10

Share this review:

Best platform I've found!

Reviewed a year ago

Great overall experience - support is amazing - makes sure it works, knows how to fix whatever you've done wrong and make things work in moments. Uptime is phenomenal.

Pros

It's a cut and dry VoIP service that provides exactly what I need, how I need without burdensome interfaces.

Cons

Needs a little more public info on new features with clear pricing such as virtual PRI's where you can figure it out yourself without having to contact sales.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

VOIP.ms

Reviewed a year ago

General experience has been great. Our telephone spend is less than 10% of what it was with traditional phone service providers.

Pros

If you know what you are doing this offers great value for money. An initial challenge is working out the per minute pricing model for voip services. However, it is invariably way cheaper than any other phone model.

Cons

Definitely this system is NOT for the technically 'faint of heart'. You need to get your hands dirty but once you do, no problem.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend5/10

Share this review:

Review of VOIP.ms

Reviewed a year ago

We are able to have a VOIP system over a very slow DSL internet connection because this voip system is not big and bulky. Overall, it works well enough.

Pros

It is a powerful software that gives lots of options and functionality with VOIP. It is lean and does not have a lots of bulk so it can be used over phone lines without using lots of bandwidth. The wiki is helpful and the customer service has always been willing to help. It is great that you don't need to purchase customized equipment to use VOIP.ms. Now with the self isolation it has been great to have the option to forward the phone numbers.

Cons

- There are lots of dropped or lost calls - There are lots of unconnected calls - At times the quality of calls are very poor - It is complicated to make changes and not always clear the order or process - The registration of users is not always clear - Sometimes there is a problem, but I don't know all the technical terms to ask about the problem.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

VOIP.MS, the best voip solution for both individuals and businesses, hands down.

Reviewed a year ago

Originally, I had sought out a way to keep my own land line number. After using VOIP.MS for a while and realizing how simple and rock solid it was, I began transitioning my family off of the expensive telco's and into sub accounts on VOIP.MS. They can't tell the difference (it just works) except for the huge savings they're seeing. I am now transitioning our small church to VOIP.MS and expect to save several hundred dollars a month for them. Tech support has always been responsive. Feature requests are always considered, though to be honest, most of things I have requested were already available and I just didn't realize!

Pros

A vast array of features that, while overwhelming at first, are fully explained and easy to implement with the great support site and help files. And you can beat the pricing. Anywhere!

Cons

Because there are so many features and tools, the dashboard can be quite intimidating.

Vendor response

Hi Matt, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Great Service with Ease

Reviewed a year ago

They have helped many times where there are difficulties. It works great for our office.

Pros

I love the simplicity of their platform. Its easy to setup and get going right away. They provide guides for those who need them and they also help out where they can for your own platforms.

Cons

I think they could update the backend side a bit more for ease of use but otherwise it works.

Vendor response

Hi Brendan, thanks for being a VoIP.ms customer, we appreciate your honest feedback.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Saved money and got better service

Reviewed a year ago

I would never consider using another provider. The VoIP space has a lot of companies that mark up the near-zero cost of PSTN connectivity, charging outrageous per-user fees, billing for services you don't care about or use. VoIP.ms has built an incredible automated platform that is designed to reduce costs without sacrificing availability, and then passes those savings on to their customers. I've worked with companies that reduced their expense on phone service by a factor of 20 by switching to VoIP.ms. No one ever leaves this service.

Pros

Flat rates for DIDs. Per-minute pricing with per-second billing. Self-service. Lowest prices. Great documentation. Rock-solid uptime. Cost only goes down.

Cons

Some features can be difficult to use. Options are open-ended, and the best configuration for you is likely to be a matter of opinion. Support is typically email-only.

Vendor response

Hi Andrew, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Viop.ms Benefits

Reviewed a year ago

Perfect fit for my home, and office, even for my customer. Well document configuration manual. and lots of feature right off the provider side, I have a few customer that just needs a conditional forwarder, and I was able to set it up right from Voip.ms no need for PBX.

Pros

The part that I liked the most about this software is the reselling portal, just make it so easy to setup a new account and start belling them for their usage. All the basic feature are there for setup a call forward or a fail-over is the PBX goes down. super low rate! as low as 0.009 per minute.

Cons

Only offer pay per use on outbound call. not such a big deal since their rate are so low.

Vendor response

Hi, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Voip.ms is awesome

Reviewed a year ago

We switched from an on premise to a PBX to voip.ms. It was an extremely easy transition. The moving of our DIDs, setting up our extensions, linking them to our phones, it was all very easy. Configuring the IVR, adding the voice prompts. All very easy. Support is awesome.

Pros

I have been using voip.ms for years, both at the office and at home. We have had no issues, and their support has been really good. They have been very responsive, and gave the extra support that was needed to troubleshoot any issues.

Cons

My only issue is that with the account setup, extensions are defaulted to account_extension, which is annoying but I understand it from a technical perspective.

Vendor response

Hi Fawad, thanks for being a VoIP.ms customer, we appreciate your honest feedback.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend9/10

Share this review:

Pro and cons using voip.ms

Reviewed a year ago

I have nice and competent service by chat, this is the strenght of voip.ms,

Pros

Easy of administration, allow to have multiple account so i connect multiple phones systems Stability, no issue with upgrade or bad software version

Cons

Fax service is not reliable, the billing in US dollars. SMS services will need a nice android and ios interfaces.

Vendor response

Hi Jean-Francois, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Incredible Product! Best VoIP Provider Out There!

Reviewed a year ago

Managing Voice calling and voice messaging.

Pros

Incredibly great service and support. Price is a great deal! Tons of features! Easy to use!

Cons

I cant think of anything. I am incredibly satisfied with VoIP.ms.

Vendor response

Hi Mark, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

great voip service - aimed at technical consumers more than 'end users' to some extent

Reviewed 9 months ago

voip MS is stable / good service. I started using it for my own business use primarily, and then over a period of 5 years I have deployed numerous clients onto VOIP system built around VoipMS platform, with me acting as the service provider/reseller. It is possible to offer a good quality service, with reasonable markup, and still give clients a phone system offering that is *FAR* less expensive than traditional telco or 'standard modern voip system pricing' even. ie, most 'big' voip providers who sell direct to consumers, tend to sell for a much higher price point.

Pros

features are good, price point is very good, they keep adding new features gradually as time passes. The core PBX is sufficiently feature rich to use for modest size deployments (20-ish handsets) and if you need something bigger/fancier then just deploy a PBX Cloud Hosted VM and use VoipMS as your sip trunk provider to feed service to your custom PBX. Support team is responsive to email support queries. Overall the offering is excellent value. Once deployed it tends to "just work" very consistently / reliably.

Cons

learning how to use the web-admin interface is a bit confusing at first, but once you learn it - it is lean, efficient, easy to use. there are occasional drop calls or call quality issues, but these are very infrequent and most often have to do with problems 'client side' (ie, Busy LAN at client site > congestion > can cause poor call quality if the client site firewall is not setup to do QoS suitable for triaging Voip traffic above other traffic). So this is not a problem with VoipMS so much as a problem with 'insufficiently well configured client sites' or 'sites which lack adequate ISP bandwidth' etc.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend9/10

Share this review:

Excellent VoIP service for SME

Reviewed a year ago

We moved from a traditional phone provider charging around $30 per month per line (2 lines) to VoIP.ms. It now cost us in average 5$ per month for calls, DID and e911. Considering that I was never calling my provider tech support and that I had to buy for $500 worth of VoIP equipments (PBX, phones), we started saving after about 9 months and got immediately a load of features that we did not have before: call transfer, IVR, simultaneous inbound/outbound calls, etc. After about 12 months of usage, we have the same reliability and call quality as we had with the traditional provider with much more flexibility. We are very satisfied.

Pros

- Very good reliability. I had only a few minutes of unplanned downtime caused by their infrastructure in the last 6 months. - Excellent communication from the provider when they are planning maintenance. - Great offer of VoIP features, more features than most self-service VoIP providers. - Features are easy to configure if you have some basic knowledge of VoIP concepts. - Cost is very competitive and they are not hiding any fees, every one-time and recurring cost is clearly shown. - No additional cost for call features such as caller id display, call filtering, voicemail, etc. - Free calls between VoIP.ms customers - Very responsive technical support - Detailed billing showing exactly what you pay for. - A lot of points of presence over North America minimizing latency

Cons

- All VoIP features are there but lacking some customization options. For those who need advanced customization, it is just better to install a local PBX and use VoIP.ms as a simple SIP trunk provider. All other features offered by VoIP.ms is useless at this point. - No options or helping features for IP phone auto-provisionning, like config/firmware upload, TFTP, phone inventory, etc. - No easy way for trying a configuration before going to production, like obtaining a temporary phone number for dial-in testing or some way of making a snapshot (backup) of the configuration before making a bunch of changes. If you want to roll-back many changes you make, take notes!

Vendor response

Hi Jocelyn, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

I Recommend VOIP.MS many times a week

Reviewed a year ago

I changed from a different provider because of cost. It soon became obvious that I had also been missing many features which have enhanced my usage of the system. I manage websites and sell website hosting for customers and have encouraged them all to consider Voip.MS. Many now have either local or toll-free numbers with the service. Even though toll-free numbers are not required these days, they tend to show a company in a better light and look more professional. Oftentimes these toll-free numbers are chosen to spell the website, company name or function. Recent examples they used were 1-8xx-KONA-FARM for a farm which gives farm tours. I have need to open a couple of tickets and their response was quick and accurate.

Pros

Voip.MS has many free features which telephone companies charge for. The software is easy to configure and fairly intuitive. The usefulness and cost savings are one of the largest drawing point.

Cons

There are only a couple of issues I have had. One is the ability to internally call a ring group, and their time conditions are not based upon my own time zone. These are very minor issues and not deal breakers for me and I have opened Feature Requests for them.

Vendor response

Hi Mark, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Amazing Value for Money

Reviewed a year ago

I have had a great experience with VOIP.ms. I transferred my cell phone over to VOIP.ms, and saved a ton. Whenever I had a problem, I used the chat feature for help and they were able to help me figure out the issue every time, and every time the issue had to do with my setup and not the service itself. Overall, I highly recommend this service to folks, I've already signed up a few people, and they love it.

Pros

VOIP.ms provides VOIP services at an amazing price, making it the obvious choice over any other VOIP service provider. In my opinion, the top benefits are; 1) Price - this is absolutely unbeatable when compared against other options. 2) Control - all features and functionality can be completely controlled by the user. 3) Features - There are so many features included with voip.ms that there are things...

Cons

Two main cons; 1) I can't use the text features to receive MMS messages or validation codes for logging into accounts. 2) Setting everything up can get very complicated. There is an amazing wiki available, and the customer service is amazing as well which has made it possible for me to set this up on my own, but you need to be a little tech savvy to get it done.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

very good and customizable VoIP service

Reviewed a year ago

Very good overall experience. Responsive customer support. They keep improving the system and adding new features on a regular basis. The outages are rare and far between and until now there was no full outage, just regional or local ones.

Pros

VoIP.ms provide the full features you can expect from an entreprise phone system mixed with many features you expect from your mobile carrier. You can configure extensions, call waiting, trunk lines, hunting lines, call attendants, schedules and also have voice mails delivered to your email, SMSes delivered by email, on their portal or in your VoIP app. They support wide-band and narrow-band codecs. Your call setup and voice are encrypted (SRTP and SIP TLS), so you can safely take a phone call from almost anywhere without the need to route your call via a VPN. Support for porting both mobile and land-lines Canadian DIDs. Points-of-Presence in North America and Europe.

Cons

Firstly I should mention that this provider is best for advanced users, as the setup can quickly become overly complex for regular, non-IT persons. Once you are all setup, there are couple of limitations that are getting to be quite annoying after using them for a while: 1) no MMS support (not even a notification for either the sender or the receiver that the MMS is not delivered) 2) no support for receing SMS from short numbers (so you will not be able to receive your security confirmation codes unless the sender using full 10-digit DIDs)

Vendor response

Hi Andrei, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

If you're IT inclined, voip.ms is the best there is!

Reviewed a year ago

Al l in all, it's packed with features ranging from group-ring (having multiple phones ring at the same time) to full Virtual Receptionist (on-hold music included!). It supports soft-phones (I use jitsi), IP phones (I have Cisco phones), Cell phones, Landlines (you can add "standard" phone numbers to ring-groups for instance), and PBX (I do not use this feature, but it's there). They offer support but I do no recall using it. The system just works. Documentation is clear and precise (they offer guides to configure pretty much everything you can think of).

Pros

Not only did it fit my needs about 10 years ago when I began using the service, but they keep improving it, adding features months after months. I just started using the call recording feature this month! IVR works like a charm; managing recordings is straight forward as well.

Cons

It can be intimidating to setup at first. I personally don't mind, but I wouldn't recommend it to the average grand-mother.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

DIY Full-Featured VOIP at a Great Price

Reviewed a year ago

VoIP.ms powers all of our individual phone lines as well as our sales and customer service phone trees (IVR). We also use it for text messaging with customers.

Pros

VoIP.ms is totally customizable and has more features than the major brand-name voip SaaS platforms, at a fraction of the cost. All of our users can pick their own setup (physical VoIP device, softphone, call forwarding) and change whenever needed. Call quality is consistently great (much better than previous companies we tried) and we've never experienced an outage.

Cons

There is a learning curve to the admin panel but that's balanced by the potential for customization.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Good VoIP service for technically inclinded users

Reviewed a year ago

Voip.ms offers me the flexibility to route incoming calls to phones, mobiles, or voice mail depending on the caller and the time of day. It also offers cheap outgoing calls. As a small company there are many features we don't use (we don't have a call center or multiple sales agents), but I can see these would be useful if we had more staff. If you are unfamiliar with VoIP you do need some technical knowledge for set-up, but there is lots of technical support around and a useful technical support wiki.

Pros

Voip.ms offers a flexible bring-your-own-device service for Voip - which means you only pay for what you use, and you can combine their services with others if another VoIP provider provides a particular service you need or provides a better termination rate to some destinations. Once set up, there is little to administer, and it is easy to examine tor export the call detail register to look for abuse or savings.

Cons

Although incoming robocall numbers can be blocked, the mechanism for doing this is quite awkward, requiring copy and paste operations from the CDR (Call Detail Record) into another form, and adding the number to a group in a phone directory. A dedicated block list is really needed for this use case. A feature to be aware of is that you get to choose between "Premium" and "Value" for outgoing calls, with improved service guarantees for "Premium". Both have always worked well for me, but depending upon your destination the "Premium" may sometimes be cheaper than the "Value" routing. If you make a large number of calls to international destinations, it's worth checking which routing which routing is appropriate.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Great value business and home phone VoIP system

Reviewed a year ago

Tech support is quick to respond, overall very satisfied with support. Number porting goes quickly and with out issue typically. I would love to see an app for this service, haven't tried 3rd party VoIP phone apps with it yet but I think it has great potential as an enterprise system with the ability to compete with Nextiva, RingCentral, etc. if it just had a pre-packaged app to offer.

Pros

Extremely low cost, only about 5% of the cost of many competitors. Reliable enough for Fire/Alarm systems and daily use for the entire company! Configurations have a bit of a learning curve, but much of the documentation has been updated recently which helps. Offers many features only found on much more expensive systems such as SMS, Call Recording, etc. but many are in beta. Ring Groups, e911, voicemail to email are all working great and well established. Low cost reliable phone system for your business!

Cons

Occasionally issues with Polycom VVX series going offline, or needing to switch servers. May be related to a configuration issue/template, as I don't have this issue with any other hardware. Grandstream devices seems to be the most reliable, the best just FYI for whomever reads this.

Vendor response

Hi Sam, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

VOIP.ms review

Reviewed a year ago

We are happy with their service. The telephone help line is good. The last while, we found the chat line is just effective.

Pros

The fact that everything to do with my PBX is in the cloud is a big plus. The whole system is feature rich, the IVR, the time conditions, evening buying new phone numbers are easily done.

Cons

We have been a client for over 5 years now. I can not think of any instances where we are not happy with the system. In fact, some frustrations often turn out to be our own user set up errors.

Vendor response

Hi David, thanks for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

A small business experience with VoIP.ms

Reviewed a year ago

We ported existing telephone numbers to VoIP.ms 5 years ago. We added a fax number this year. In the first year we experienced technical issues with analog telephone adapter configuration and router compatibility. We resolved this by switching internet provider as well as with online and personal support from VoIP.ms. In addition to the traditional analog telephones, we also use a 3rd party soft-phone interface that works very well.

Pros

Flexibility, price and stability are my top 3 likes about the VoIP.ms service.

Cons

At the current time there is nothing that I dislike. Five years ago, when we first started, there were technical issues. They have since been resolved with help from the excellent VoIP.ms support team.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

If you know a bit about VoIP/SIP in general, VoIP.ms is amazing.

Reviewed a year ago

Initially we ran our own Asterisk server, both inhouse and hosted, with mixed results. We used trunks and termination through multiple providers, and generally liked the flexibility. Asterisk is great, to a point, that point hit us when we were looking at an upgrade that changed around some internals and our poor design decisions started to bite us. Fine. We were using VoIP.ms just for trunking,...

Pros

For small to medium business use VoIP.ms is awesome. We started using purely for trunking and termination, but it now replaces our local Asterisk environment almost completely.

Cons

The documentation is thorough, but sometimes slightly out of date and it it sometimes requires a bit of technical knowledge to find and understand the right article. This is fine, just understand VoIP.ms is best for wholesale or technical users.

Vendor response

Hi Dave, thank you for being a VoIP.ms customer and for your honest review!

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

The fastest, easiest and cheapest VoIP service, full-featured, no vendor lock-in.

Reviewed a year ago

I've been using VoIP.ms since the beginning. As a VoIP specialist, I helped many companies migrate their old phone systems. I'm also using VoIP.ms at work to test out products (Mediatrix ATAs and SBCs). Finally, I also use it at home: my 4102 ATA has one line going to my office PBX and the other has a VoIP.ms number, mostly for my kids, and when I need to make a private call.

Pros

Couldn't be more easy to setup. It takes a few minutes to create a free account, then you can easily configure your device, softphone, PBX or SBC. You can pre-pay your account with a minimum $15 Paypal payment (non-recurrent) and start making calls for less than a penny per minute. You can port your old phone number or get a new one from virtually any regional code in Canada/US and several countries around the world. It has voicemail, forwarding, IVR, sub-accounts, extensions, name it!

Cons

Seriously, it's hard to find things I don't like about VoIP.ms... About the only negative point is that the login is tied to a single mail address, and there's no notion of technical contact/admin contact, which created a few problems as an IT guy supporting several customers. There's a reseller feature, but in my case I just want to help for the initial setup and not have to deal with monthly billing.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

Great voip provider with even better service!

Reviewed a year ago

Honestly I love everything about using VoIP.ms from the platform to the product to the support. They are always there to provide support if you need it, although I rarely need it because the platform is really great and stable.

Pros

I love the fact that they are really easy to setup and use. I use it more for personal use and absolutely love how I can stay in touch with my family for a fraction of the price. Ive set it up for many family members and even provided them with simple instructions and they were able to set it up for themselves without issues.

Cons

I wish that instead of having multiple servers in the same location they had 1 customer facing server and they had multiple servers behind the scenes. That would make life easier in case there is an issue with one of the servers. Would also love if they had an iOS App that would be amazing and make life easier when making calls.

Overall Rating
  • Value for money
  • Ease of use
  • Features
  • Customer support
  • Likelihood to recommend10/10

Share this review:

VoIP.ms

Reviewed a year ago

As a sole proprietor of a small business, I was looking for an inexpensive but reliable telephone service. I am fortunate enough to have solid and reliable upload and download from my Internet Service Provider, so VoIP made good sense for me, and VoIP.ms in particular offered the most flexibility for the best price.

Pros

I appreciate the flexibility to use my own VoIP client or device with the service, and the ease with which I can set it up. The available Wiki articles provide instructions for a myriad of different clients and devices. I also need to give a shout-out to the online chat support team, who are responsive and knowledgeable.

Cons

The only shortcoming of the service that I've found is related to the Audio Conferencing feature. The issue is called "talk-off", whereby an inflection in a conference participant's or administrator's voice inadvertently triggers the mute function. This is an ongoing issue, which could be easily overcome by changing the feature access code from a single digit ("1" in this case) to two sequential digits (such as "*1").