Somewhere in your office there is a phone system. Maybe it is a box on the wall, maybe it is a cloud service with desk phones, and maybe nobody remembers who set it up. Meanwhile your team spends all day inside a collaboration app: chat, meetings, files, shared channels. A fair question follows. Why are those two things separate?
They do not have to be. Microsoft Teams can carry your regular business phone line, so the app people already have open answers the calls that used to ring a desk phone. That is a genuinely good fit for a lot of small businesses and a genuinely poor fit for some others. Here is how to tell which one you are, without the sales pitch.
What “Phone System Inside the App” Actually Means
Two separate things are happening, and mixing them up causes most of the confusion.
The first is call control: ringing, holding, transferring, voicemail, auto attendants that answer with a menu, and call queues that ring a group. That lives in the app. Microsoft’s documentation, as we read it in 2026, describes connecting phone numbers to Teams so people can make and receive calls “from the Teams app across desktop, mobile devices, certified Teams phones, and meeting room devices,” including support for voice applications like auto attendants and call queues.
The second is the dial tone itself, the connection to the public phone network so you can call anyone in the world. That comes from a carrier. Think of the app as the handset and switchboard, and the carrier as the wire leaving the building. You need both.
The Licensing Question, in General Terms
Licensing changes often enough that any specific price here would be wrong within a year, so learn the shape of it and confirm current details with Microsoft or your provider before you budget.
The shape is this. Microsoft states plainly that to use phone network calling, “the user account must be licensed with the Teams Phone application and also be equipped with a PSTN solution from your PSTN service provider of choice.” One license turns on the phone features. A second arrangement provides the dial tone. Microsoft’s documentation describes several ways to get that second piece.
- Microsoft as your carrier. Microsoft describes this as a cloud based phone solution “with Microsoft as your operator,” where phone numbers, network access, and support all come from Microsoft. Simplest to buy, fewest moving parts.
- A certified partner carrier. Microsoft describes using “certified third-party landline operators who have already completed the PSTN integration,” which means you contract with a telecom company and the connection is prebuilt. Often better rates and a local account rep.
- A mobile carrier arrangement. Here the number on a person’s mobile SIM doubles as their business number. Microsoft’s documentation notes this option “doesn’t support Audio Conferencing or voice application numbers,” so check the limits carefully.
- Bring your own carrier. Microsoft says this option works with “any PSTN operator” and is achieved through a certified session border controller “that is procured, installed, and managed by you.” Most flexible, most technical, and it puts a piece of equipment back in your closet.
The right choice usually comes down to how many numbers you have, whether you are attached to your current carrier, and who you want to call when calls stop working.
Where It Shines
We recommend this setup most often in three situations.
- Your team already lives in the app. If people are in chat and meetings all day, adding calling removes an entire device and an entire habit. One place to look for a missed call, one voicemail box, one set of contacts.
- Your call flows are simple. A main number, a short menu, a few groups that ring together, and voicemail to email. That is most small businesses, and it is exactly what the built in tools handle well.
- Your people move around. Remote staff, hybrid schedules, technicians in trucks. The business number follows the person to a laptop or phone instead of sitting on an empty desk.
There is a quieter benefit too. One fewer vendor, one fewer bill, one fewer admin portal, and one fewer system to patch. That is the kind of time saving we argued for in our post on why saving time takes priority over saving money.
Where a Traditional Phone System Still Wins
We will say the unpopular part. Sometimes the answer is no, or not yet.
- Real call center work. If you need supervisors listening in live, detailed queue statistics, callback in queue, and screen pops tied to your customer records, look hard at purpose built contact center software before assuming the basic tools cover it.
- Heavy front desk duty. Someone answering constantly, transferring blind, and watching who is available often wants a physical console with real buttons. It can be done in software, but test it with the actual person before you commit.
- Specialty hardware. Overhead paging, door intercoms, credit card terminals, and older analog devices need specific gateways or adapters. Confirm supported models before you cancel anything.
- Elevator and alarm lines. These are usually separate circuits with their own monitoring and code requirements. Never cancel them as part of a phone migration without asking your elevator and alarm vendors in writing.
- Emergency calling details. Microsoft’s documentation states that each Calling Plan user “is automatically enabled for emergency calling and is required to have a registered emergency address associated with their assigned telephone number,” and that in the United States and Canada an emergency location is required when a number is assigned. Addresses for mobile staff deserve real planning, not a checkbox.
The Network Requirement Nobody Wants to Discuss
Calls in an app ride your internet connection, which means call quality becomes an IT problem instead of the phone company’s problem. The good news is that voice is light. Microsoft’s network guidance, as published in 2026, lists 58 kilobits per second in each direction as the recommended bandwidth for a call, which is small next to video. Microsoft also notes that when bandwidth is insufficient, Teams “prioritizes audio quality over video quality.”
Consistency matters more than raw speed. Microsoft recommends routing this traffic around the company VPN, noting that VPNs “are typically not designed or configured to support real-time media” and that some may not support the protocol calls rely on. Microsoft also recommends quality of service settings “on all segments of a managed network,” and treats Wi-Fi planning as an important part of a high quality deployment. In practice, most bad call complaints we investigate trace back to a crowded wireless access point, a VPN, or a cheap headset rather than the phone service itself.
One more honest note. When calling lives in a cloud service, an internet outage takes the phones with it. Have a plan for that, whether it is a second connection or forwarding the main number to cell phones. We wrote about that dependency in the cloud can go down and what that means for your business.
The Bottom Line
Running your phones inside the app your team already uses removes a whole layer of equipment and habit, and for a typical office with straightforward call flows it works well. It is a weaker fit for busy front desks, real call centers, and buildings full of specialty wiring. Decide based on how your people actually answer the phone, not on how the demo looked, and confirm current licensing before you sign anything.
If you want a straight answer about whether this fits your business, we will map your current call flows, check your network, and tell you honestly if you should stay where you are. Contact us today.
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