Teams Phone vs a legacy PBX: is it worth migrating?

The traditional phone system — the physical PBX in the rack room — still works in many companies. But the desk phone increasingly competes with an awkward question: why keep a separate system when Teams, where people already meet and chat, can also be the phone? That is what Teams Phone proposes. Is it worth it? It depends on a few concrete factors.

What Teams Phone is

Teams Phone turns Teams into a full corporate phone system, with real numbers, public switched telephone network (PSTN) calling, call queues, auto attendant, transfer, hold music, voicemail and more — all integrated into the same chat-and-meetings app.

There are three main ways to connect Teams to the public phone network:

1. Microsoft Calling Plans — Microsoft provides the numbers and minutes. Simple, but subject to regional availability.
2. Operator Connect — a partner carrier provides the line, integrated natively into Teams.
3. Direct Routing — you connect your own telephony provider via a session border controller (SBC), keeping existing contracts.

In many markets, Direct Routing and Operator Connect are the most-used paths, letting you leverage local carriers and competitive plans.

Traditional PBX vs Teams Phone

Where Teams Phone shines

• Hybrid work: a person's number rings on the phone, the laptop and the headset, whether they are in the office or at home.
• Consolidation: one fewer vendor, one fewer contract, one fewer support team.
• Modern features: voicemail transcription, calls that become a meeting in one click, integration with the company directory.
• Elastic scale: adding 20 extensions is adding 20 licenses, not buying hardware.

When a PBX still makes sense

Not every case is an immediate migration. A PBX stays relevant when there is:

• A large fleet of analog phones (gates, elevators, equipment) that depend on physical lines — though gateways solve much of this.
• Long contracts with early-termination penalties not yet expired.
• Very complex call centers, which may need dedicated contact-center solutions (Teams integrates with several of them).

In those cases, coexistence is the path: Teams Phone for office staff, PBX or a dedicated solution for the specific scenario, migrating in stages.

Migration roadmap

1. Inventory of extensions, numbers, queues and devices.
2. Choose the connectivity model (Calling Plan, Operator Connect or Direct Routing).
3. Port the numbers to the new environment.
4. Configure auto attendants, queues and calling policies.
5. Pilot with one department before the general rollout.
6. Phased migration and decommission of the old PBX.

Project timelines vary widely with porting and complexity, typically from a few weeks to a couple of months.

Key takeaways

• Teams Phone turns Teams into a full corporate phone, with no physical PBX.
• Connectivity via Calling Plan, Operator Connect or Direct Routing.
• Clear gains in hybrid work, consolidation and elastic scale.
• A PBX still fits scenarios with many analog lines or active contracts — use coexistence.
• Number porting and a pilot are critical project steps.

As a CSP partner and Microsoft Solutions Partner, RHC plans and executes Teams Phone migrations, including the connectivity model, number porting and configuration of queues and attendants.