If your business already lives in Microsoft Teams, a separate phone system means a second bill, a second app, and desk phones tied to one location. Teams Phone puts calling into the app everyone already uses, on laptops, mobile phones, and certified desk phones. The migration itself is mostly planning. The technical work is quick. The porting timeline and the call flows are where projects slip.
The pieces you need
| Piece | What it is |
|---|---|
| Teams Phone license | Adds calling to a user's Microsoft 365 license. Included in E5, and an add-on for Business plans. |
| PSTN connectivity | How calls reach the phone network: a Microsoft Calling Plan, Operator Connect, or Direct Routing |
| Phone numbers | Ported from your current provider, or new numbers |
| Resource accounts | Special accounts for auto attendants and call queues. They use a free Teams Phone Resource Account license. |
| Emergency addresses | Registered locations for emergency calling |
Choose your PSTN option
| Option | How it works | Fits |
|---|---|---|
| Calling Plan | Microsoft is your phone carrier, bought as a license | The simplest option for most small businesses |
| Operator Connect | A participating carrier connects to Teams, managed from the Teams admin center | When you want a specific carrier, better rates, or coverage Calling Plans don't offer |
| Direct Routing | Your own SBC (or a hosted one) connects Teams to any carrier | Complex needs, unusual locations, or keeping an existing SIP contract |
Inventory before you port
Most surprises come from lines nobody remembered. List every number on the current system:
- Main line, direct lines, and fax numbers
- Alarm panels, elevator phones, door buzzers, and credit card terminals on analog lines. These don't move to Teams without an analog adapter or a separate solution.
- Numbers that forward somewhere, and toll-free numbers
- Current call flows: business hours, holiday routing, menus, and who rings for what
Number porting
Porting moves your numbers from the old carrier to the new one. In practice:
- Submit a port request with a Letter of Authorization and a recent bill from the current carrier. The name, address, and account number must match exactly.
- The losing carrier validates it. Mismatched details are the number one cause of rejected ports.
- You get a firm order commitment (FOC) date for the cutover.
- On that date, the numbers move. Assign them in Teams right away.
Call flows
Rebuild call routing in the Teams admin center:
- Auto attendants: menus ("press 1 for sales"), business hours, holidays, and directory search
- Call queues: groups of people who answer, the routing method, overflow, and timeout
- Resource accounts tie a phone number to an auto attendant or queue
Map every existing call flow on paper first. Don't redesign and migrate on the same weekend. Match what exists, then improve it once people are comfortable.
Emergency calling
Emergency calling rules apply to business phone systems, and Teams supports dynamic emergency calling, which detects a user's location from network information. At a minimum:
- Every office has a validated emergency address in Teams
- Users working from home know how to set their location in Teams
- Security desk or reception notifications are configured, if required
Devices and cutover day
- Headsets for everyone who takes calls on a laptop. This matters more than any setting.
- Certified Teams phones for reception, shared spaces, and anyone who wants a desk phone. Common area phone licensing covers lobby and break-room phones.
- Cutover day: test inbound and outbound calls on every ported number, every auto attendant path, and emergency calling (using the test number your provider supports, never a real emergency call).