What it does

A participating mobile operator makes the user's company SIM number their Teams number as well. Calls can be made and answered on the phone's native dialer or in Teams, and moved between the two mid-call without dropping. It's provisioned through the same operator model as Operator Connect.

Key facts

• Prerequisites: a Teams Phone licence, an eligible mobile subscription with a participating Teams Phone Mobile operator, and the user in TeamsOnly mode. The whole organisation doesn't need to be TeamsOnly.
• Enabled from Voice > Operators in the Teams admin center — pick an operator that offers Teams Phone Mobile, select countries, give contact details, accept the data transfer notice.
• The operator provides the SIM-enabled numbers and uploads them to the tenant. Users can get new numbers or port eligible existing ones, via the operator.
• User numbers only. Teams Phone Mobile numbers can't be used for Audio Conferencing or for voice applications (auto attendants, call queues).
• Incoming call preference is controlled by the Teams mobility policy: New-CsTeamsMobilityPolicy -MobileDialerPreference Teams|Native|UserOverride, assigned with Grant-CsTeamsMobilityPolicy. Default behaviour rings the Teams app first.
• Whichever preference is set, other Teams endpoints ring simultaneously.
• Native dialer calls still show Teams presence as in a call, and land in combined call history and unified voicemail.
• Moving a call into Teams brings in video, content sharing, recording and transcription. Compliance recording is supported where the right subscriptions exist.
• Emergency address handling follows the operator model (operator assigns, you assign, or operator assigns and locks). Native dialer emergency calls can use the location the mobile network has.
• Can sit alongside Operator Connect and Direct Routing in the same tenant, and be rolled out to selected users only.

When to use / skip

This is for people whose mobile is their main phone — field sales, execs, frontline managers — who currently juggle a desk number and a mobile number. Giving them one number with Teams presence, recording and history across both is a real improvement, and it's the only PSTN option that properly handles the "calls made from the native dialer" problem for compliance.

Skip it if the client's mobile contract is with an operator that doesn't offer it in their country (operator availability is the gating factor, not Microsoft), if users are on BYOD personal SIMs, or if the population that would benefit is small enough that a Teams app on the mobile with a desk DDI does the job. Also skip it for anything that needs to be a service number.

Configuration decisions

• Which users get it — usually defined by role, and often tied to the mobile fleet refresh.
• Dialer preference per group: Teams first for the people who want the full Teams experience, Native for people who live in the dialer, UserOverride when you'd rather not fight about it.
• What happens to their existing desk DDI — release it, keep it as an alternate, or port it away.
• Emergency address model the operator uses, and how remote and mobile users are covered.
• Whether compliance recording needs to cover native dialer calls, and whether the recording vendor and operator both support it.
• Voicemail ownership — the operator's network voicemail vs Teams unified voicemail. Get this clear in the order with the operator.

Gotchas

• Availability is per operator and per country. A client with a pan-European fleet on several carriers will usually find only some of them can provide it.
• The mobility policy isn't the same thing as calling policy — people set unanswered/forwarding rules in calling policy and expect them to change which dialer rings. They don't.
• Users who already have a Direct Routing or Calling Plan number need it unassigned before the mobile number can take its place. Sequence the change.
• Emergency behaviour differs depending on whether the call starts in the native dialer or in Teams. Test both on the same device.
• Porting a personal mobile number into a corporate subscription is a commercial conversation with the operator first, and a Teams task second.

Consultant notes

• Run a pilot of ten or so heavy mobile users before committing. The value shows up in their call history and missed-call complaints, not in a demo.
• Get the operator's onboarding guide — it'll tell you about SIM provisioning, eSIM support and voicemail that Learn doesn't.
• Agree the default dialer preference with the business, not IT. It's the single most visible choice for users.
• Document which users are on Teams Phone Mobile in the number inventory — they show up in the admin center but are easy to lose in a big estate.

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Recheck the operator directory and the mobility policy options before scoping any new country