How do we replace our phone system with Teams Phone?

Key facts

• Discovery of numbers, carriers, devices and call flows is the step most likely to be skipped and the one that causes most cutover problems.
• Rebuild call flows in Teams rather than copying every legacy menu; most PBX menus have grown stale.
• Analog devices such as fax, door phones and paging need a plan before cutover.
• Pilot one site first and move the headquarters or busiest site last.
• Do not cancel old carrier service until every number has ported and been tested.

Step 1: Inventory what you have

A phone system holds years of decisions nobody wrote down. Before anything is configured, build a complete inventory. It becomes the source of truth for licensing, porting, call flow design and testing.

• Every phone number, its carrier, account and billing telephone number, and what it rings today.
• Main lines, auto attendant menus, hunt groups, after-hours rules and holiday schedules.
• Shared phones in lobbies, warehouses and break rooms, and who answers them.
• Analog lines: fax, alarm panels, elevator phones, door entry, overhead paging.
• Integrations: contact center software, call recording, CRM click-to-dial.
• Emergency calling: each site's address and how 911 calls are handled today.

Step 2: Choose the PSTN connection and licenses

Teams Phone needs a PSTN connection: Microsoft Calling Plans, Operator Connect through a participating carrier, or Direct Routing through a session border controller. The inventory decides this. Sites with paging, fax or a contact center integration often point toward Direct Routing or an operator that supports analog lines.

License every calling user for Teams Phone, plan resource accounts for auto attendants and call queues, and decide which shared spaces need common area phones or Teams Rooms. Check that your network, Wi-Fi and internet circuits can carry voice, and set up quality of service where you control the network.

Step 3: Rebuild call flows in Teams

Translate how calls should flow, not how the old system happened to be set up. Auto attendants handle menus, business hours and holidays. Call queues distribute calls to agents with routing methods such as attendant, serial, round robin or longest idle, and handle overflow and timeout.

Review each legacy menu with the people who answer the calls. Many organizations remove options nobody uses and shorten menus. Build and test the flows on temporary numbers before porting the real ones.

Step 4: Pilot, then move site by site

Pick a small, forgiving site or team as the pilot. Assign numbers, deploy headsets and desk phones, train users, and run real calls for a week or two. Use Call Quality Dashboard and user feedback to fix network and device issues before wider rollout.

Then schedule the remaining sites in waves. Moving the headquarters or main reception line last means the most visible number moves only after the process has been proven.

Step 5: Port numbers and cut over

Number ports run on the carrier's schedule. Submit port requests with accurate account details, confirm the firm order commitment date, and plan cutover for that day with staff on hand to test inbound and outbound calls, the main line, queues and 911 address assignment.

Keep the old system and carrier service active until every number has ported and been tested. Only then cancel lines and decommission the PBX. Update published numbers, voicemail greetings and any systems that dial out.

Common pitfalls

Most PBX replacements that go badly fail on details rather than technology.

• A forgotten fax or alarm line stops working on port day.
• Wrong billing telephone number or account name delays the port.
• Emergency addresses are not assigned, so 911 calls lack a dispatchable location.
• Users get no training on transfer, park and voicemail, and call handling suffers in week one.

How Accred Consulting approaches it

Accred Consulting runs a phone system replacement as a defined project. Discovery inventories numbers, carriers, devices, analog lines and call flows, and the proposal sets scope, fixed price and timeline. The US-based specialists assigned to your engagement design the PSTN connection, rebuild auto attendants and call queues, configure emergency locations, and pilot one site before moving the rest in waves. In one engagement, four sites moved from a PBX to Teams Direct Routing with the pilot site first and HQ last. Handover includes documentation and knowledge transfer, with optional support retainers.

Track record: 475+ client projects, 2,000+ migration workstreams and 210,000+ users migrated by a US-based team. Company facts · Case studies

Related questions