Multi-Line Comes to Microsoft Teams Phone: What It Means for Enterprise Migrations

For anyone who has spent time helping organizations move off legacy phone systems like Cisco CUCM or Avaya, you know the conversation that always came up: ​“But what about our multi-line users?” It was one of the stickiest objections in the Microsoft Teams Phone migration playbook. That objection just lost most of its teeth.

Microsoft has begun rolling out native Multi-Line support for Teams Phone (MC1261591). It removes one of the last real blockers to using Teams Phone as a full PBX replacement.

What’s Actually New

Multi-Line lets a single Teams user hold up to 11 phone numbers - one primary, one private, and up to nine alternates. When placing outbound calls, users see a ​“Call As” dropdown in the Teams dial pad and choose which number to present as their caller ID.

The flexibility is in how those numbers are sourced. You’re not locked into a single PSTN connectivity type. A user’s lines can be a mix of:

• Direct Routing
• Operator Connect
• Calling Plans
• Teams Phone Mobile (one per user)

This hybrid assignment wasn’t possible before. It opens up practical architectural options for complex enterprise environments.

Here are the key behaviors to understand about Multi-Line:

• The primary number must be assigned and match the user’s usage location (applies to Operator Connect, Calling Plans, and Teams Phone Mobile)
• A user can hold up to 11 numbers total: 1 primary + 1 private + 9 alternate
• Only 1 Teams Phone Mobile (TPM) number is allowed per user
• Alternate numbers can be from any region or type (Direct Routing, Operator Connect, Calling Plans, Teams Phone Mobile)
• Inbound calls display which specific line is being called, so users always know which number was dialed
• Users can select their outgoing number when placing calls, except on SIP desk phones
• The following features apply at the user level only, not per line: Voicemail, Delegation, Call Group, and Call Settings
  

Getting It Configured

The Teams Admin Center UI has reached feature parity. If the new Alternate phone number interface isn’t showing in your tenant yet, PowerShell (v7.6.0+) is your path forward.

To bind an alternate number to a user:

• GUI: Similar to the primary line assignment process, but per-line policies must be assigned after the alternate line is added.

Here’s the PowerShell:

Set-CsPhoneNumberAssignment -Identity user@​yourdomain.​com -PhoneNumber +1234567890 -PhoneNumberType DirectRouting -AssignmentCategory Alternate

Per-number policy assignments are handled separately:

Set-CsPhoneNumberPolicyAssignment -PolicyType OnlineVoiceRoutingPolicy -PolicyName International -TelephoneNumber +1234567890

And to audit what’s assigned to a given number:

Get-CsPhoneNumberPolicyAssignment -TelephoneNumber +1234567890

Per-Number Policy Control

One of the more useful aspects of this feature is that alternate lines aren’t just aliases - they can carry their own policy assignments, independent of the user’s primary line settings. Policies that support per-number assignment include:

This granularity matters. You can have a user’s primary line follow standard corporate routing while an alternate line behaves differently - applying international dialing permissions or routing through a specific SBC, for example.

Licensing: What You Need to Know

Microsoft’s position is straightforward: alternate lines carry the same licensing requirements as whatever capability they represent. Mixing PSTN types on a single user is supported, but the user must be properly licensed for each type in use.

If your user’s primary number is via Direct Routing and you want to add a Calling Plan number as an alternate, that user needs a Calling Plan license. Once a user is already licensed for a given PSTN type, additional alternate numbers of that same type don’t require additional licenses.

Audit your licensing posture before rolling this out broadly, especially where users will hold numbers across multiple connectivity types.

Why This Matters for Migrations

Multi-line limitations have historically been a forcing function that kept some organizations tethered to legacy PBX infrastructure. Departments running receptionist workflows, executives needing multiple direct numbers, or teams requiring distinct caller ID personas for different business units - these scenarios required workarounds or simply weren’t viable in Teams Phone.

That friction is now largely gone. Teams Phone is a more credible replacement for complex PBX environments than it’s ever been, and this update should make those migration conversations easier to close.

Important: Number Removal Behavior

Be aware of these cascading behaviors when removing numbers or users in a Multi-Line environment:

• Removing a number from a user also removes all associated number policies from that number
• Removing a user’s primary line automatically removes all of their alternate numbers as well
  

Current Limitations

The following scenarios are not supported today:

• India phone users
• CP (Calling Plan) SMS on alternate numbers
• Teams mobile app
• Auto Attendant / Call Queues (check the Microsoft roadmap for current status)
• SBA (Survivable Branch Appliance)

For further details, see Microsoft’s official documentation: Configure Multi-line in Microsoft Teams (Microsoft Learn).