Configure and Manage Teams Phone
Numbers, dial plans, and routing must all line up
Three layers must align before a user can dial out. First, the user needs a Teams Phone license plus a number from Calling Plan, Operator Connect, Direct Routing, or Teams Phone Mobile. Second, a dial plan normalizes what the user types into E.164; a four-digit extension 1234 becomes +14255551234 through the rule ^(\d{4})$ mapped to +1425555$1. Third, a voice routing policy connects PSTN usages to voice routes, and each route points at an SBC or gateway with a number pattern. Assign both the dial plan and the voice routing policy; a user with a number but no voice routing policy gets route failures.
Route selection. The most specific pattern wins, then route order within a usage, then usage order inside the policy. Long ordered route lists exist for a reason, and this is a frequent exam trap.
Auto attendants and call queues are backed by resource accounts, each needing a Teams Phone Resource Account license, a service number, and a Phone System license. Queues offer round-robin, longest-idle, serial, and Attract routing with overflow and after-hours handling; auto attendants can nest.
Calling policy governs forwarding, simultaneous ring, delegation, voicemail, and busy-on-busy.
Worked example. Site A's SBC fails: add a second route to Site B's SBC under the same PSTN usage and order it after the primary. No dial-plan change is needed, because reachability is a routing concern.
Rule of thumb. If the digits are wrong, it is the dial plan. If the destination is wrong or unreachable, it is the voice route.