Microsoft Teams as Your Phone System: What It Actually Takes
November 15th, 2026
"We Already Have Microsoft 365" Is Not a Phone System
Microsoft 365 gives you Teams chat, meetings, and file collaboration. It does not automatically give you a business phone number, a dial plan, voicemail, auto attendants, or 911 calling. Those capabilities come from Teams Phone and the public switched telephone network connectivity behind it. That distinction is where most Teams phone projects either succeed or stall.
Teams can absolutely replace a traditional PBX. But it is a phone system project, not a software toggle. Here is what it actually takes.
1. Licensing: What Enables Calling
Teams calling is built from separate pieces:
- Microsoft 365 license. Gives users Teams and the collaboration features they already use.
- Teams Phone Standard. Adds the phone system features: auto attendants, call queues, voicemail, transfer, hold, and calling policies. It does not include external phone numbers by itself.
- PSTN connectivity. One of three routes: Microsoft Calling Plan, Operator Connect, or Direct Routing through a carrier or session border controller.
- Devices and shared spaces. Common area phones, conference phones, and shared devices need appropriate licenses and configuration.
- Audio Conferencing. A separate add-on if you need dial-in meeting numbers.
Licensing names and availability change, and not every option is available in every market. Confirm the current bundle with your Microsoft partner before you build a budget around it.
2. Numbers and Porting
Before porting, inventory every number you own. Not just the main line and extensions - also fax lines, alarm lines, elevator phones, credit card terminals, conference bridges, hunt groups, and numbers printed on vehicles or signage.
Porting a number requires authorization, a recent bill, account details, and a letter of authorization. Timelines vary by carrier. Do not cancel the old service before the port completes. Run the old and new systems in parallel where you can, and forward calls rather than shutting anything off early.
Decide which numbers need to be ported, which can be replaced with new numbers, and which should be retired. A clean number inventory prevents the classic cutover surprise: a fax line nobody remembered is still attached to a medical office or a fire panel.
3. E911 and Emergency Calling
Emergency calling is not a checkbox. Each user needs a registered location, and the address must be correct for where they actually work. Remote and hybrid workers may need to update their location when they move. Visitors and shared devices need a plan too.
Test the process before cutover. Make sure reception knows what to do when a 911 call arrives, how the call is routed, and who receives notification. Review applicable requirements with your legal or compliance team; do not assume a desk phone's old behavior carries over automatically.
4. Network Readiness
Voice quality is network quality. Teams calls are sensitive to latency, jitter, and packet loss in ways that email and file sharing are not.
- Latency. Aim for low one-way latency; under 150 ms is a common target for good voice quality.
- Jitter. Keep variation under about 30 ms.
- Packet loss. Keep it under 1%; even small loss becomes audible.
- Bandwidth. Plan for roughly 100 kbps per concurrent call, plus headroom for meetings and normal data traffic.
- Wi-Fi. Wired connections are preferred for desk phones and critical users. If Wi-Fi is required, verify coverage, roaming, and airtime - not just signal strength.
- QoS and firewall. Mark voice traffic, prioritize it, and open the required Microsoft 365 endpoints through the firewall and proxy.
Run a network assessment and a pilot before porting the whole company. A pilot with real users on real calls finds problems while they are still cheap to fix.
5. Devices and Rooms
Teams calling works through the desktop and mobile apps, but most businesses still need physical devices:
- Headsets. The single biggest driver of user satisfaction. Test comfort, microphone quality, and compatibility.
- Desk phones. Choose Teams-certified devices and confirm firmware and provisioning support.
- Conference rooms. Teams Rooms systems need their own licensing, hardware, and room planning.
- Common areas. Lobbies, warehouses, and shared desks need devices that are easy to use and hard to misuse.
- Analog devices. Fax, alarm, elevator, and legacy phone lines need analog terminal adapters or a separate plan.
Device count is also a support question. Who provisions, updates, replaces, and troubleshoots headsets and phones after cutover?
6. Call Flows and Features
Build the call flow before you configure it. Map:
- Main number, auto attendant, and directory options.
- Department queues, ring groups, and overflow behavior.
- Business hours, holidays, and after-hours routing.
- Voicemail, shared voicemail, and transcription needs.
- Call transfer, park, delegation, and shared line appearance.
- Recording, compliance, and CRM integration.
- Contact center requirements, if any - Teams Phone is not a full contact center platform.
A diagram of how calls should move is worth more than a list of features. It exposes decisions about who answers, who backs up whom, and what happens when nobody picks up.
7. Migration and Cutover
A controlled migration usually looks like this:
- Inventory users, numbers, devices, and call flows.
- Confirm licensing and PSTN route.
- Build the call flows and test with a pilot group.
- Port numbers in batches, with a rollback plan.
- Train users on the app, headset, transfer, voicemail, and emergency calling.
- Run parallel support for the first weeks and monitor call quality.
Do not port every number on the same day. Leave room to fix routing, voicemail, and device issues before the whole business depends on the new system.
8. Ongoing Operations
After cutover, someone still has to own:
- Moves, adds, and changes.
- Number and license management.
- Call quality monitoring and carrier invoices.
- Firmware and device updates.
- Emergency address updates for remote workers.
- Security: MFA, conditional access, calling policies, and toll-fraud controls.
Teams is not maintenance-free. It is a cloud phone system that still needs administration, just like the PBX it replaced.
What It Actually Costs
The subscription is only one line. Budget for:
- Microsoft 365 and Teams Phone licenses.
- PSTN calling plan or carrier connectivity.
- Headsets, desk phones, conference room equipment, and analog adapters.
- Implementation, number porting, and training.
- Ongoing support and administration.
Teams can be less expensive than a traditional phone system, especially when you already pay for Microsoft 365. It can also cost more than expected if licensing, devices, and implementation are treated as afterthoughts. The honest comparison includes all five lines, not just the per-user subscription.
At BTS Technologies, we help Alabama businesses plan and deploy Teams-based business phone systems through TotalVoice. We handle the licensing, number porting, call flows, devices, and cutover as one project, so the phone system works on day one instead of becoming an ongoing science experiment. If you are earlier in the evaluation, our complete guide to Microsoft Teams for business covers the collaboration side.
Thinking about replacing your PBX with Teams? Contact our team for a readiness assessment and a migration plan.
Posted in: Business Phone Systems