The model
An accredited operator pre-establishes managed, redundant interconnects with Microsoft. You, in TAC: pick the operator marketplace entry, consent to data sharing, receive number ranges into your tenant, assign them like any Teams Phone number. No SBC, no certificates, no OPTIONS monitoring — those became the operator's problem, with a Microsoft-enforced quality bar (SLAs, redundant peering) as part of accreditation.
Teams Phone Mobile extends the idea to mobile: your users' MOBILE numbers become their Teams numbers — one number rings the SIM natively and Teams everywhere, call moves between cellular and Teams mid-call. Operator-dependent and the deepest carrier integration Teams offers.
What you trade
| Gain | Give up |
|---|---|
| No voice infrastructure to run | Carrier choice limited to the OC marketplace, per country |
| Operator SLA on the PSTN leg | Custom routing tricks (least-cost, legacy interop) — no SBC to program |
| Numbers self-served in TAC | Analogue devices, fax, elevator phones — SBC-only territory |
| Fast country enablement | Portability tax: leaving = number porting project per country |
The coexistence pattern is normal and supported: OC for clean countries, Direct Routing where legacy/analogue/contact-centre needs live — per-user routing decides per number.
Responsibility map (the outage argument-settler)
- Number assignment, user config, policies: you.
- Trunk health, PSTN reachability, media quality on the interconnect: operator (their portal/support owns the ticket).
- The Teams service itself: Microsoft.
- The user's network to Microsoft: you (same as every Teams call).
What to watch (proofs)
- Operator relationship state: TAC > Voice > Operators — enabled operators, country scopes, consent status; this page is your contract inventory.
- Number provenance:
Get-CsPhoneNumberAssignment | ft TelephoneNumber, NumberType, PstnPartnerName— OperatorConnect-typed numbers name their operator; the definitive "which road does this number use". - Call quality on the operator leg: PSTN usage reports + CQD filtered to OC calls — degradation clustered on one operator is their ticket, with your data attached.
- Teams Phone Mobile state: number types show the mobile variant; the operator's portal owns SIM-side provisioning telemetry.