How do we port our phone numbers to Microsoft Teams?

Key facts

• The current carrier's Customer Service Record must match your port request exactly, or the port is rejected.
• You need the account number, billing telephone number, service address, authorized name and often a port PIN.
• Porting moves numbers on the carrier's schedule; plan around the firm order commitment date.
• Partial ports can leave remaining numbers on the old account, so decide what happens to each one.
• Do not cancel service with the old carrier until the port completes.

Where the port goes depends on your PSTN option

Porting moves a number from one carrier to another. In Teams, the gaining carrier depends on how you connect to the phone network.

Gather the right information first

Most port rejections come from mismatched details. Request a Customer Service Record (CSR) from your current carrier and copy the details exactly. A recent bill helps but is not always enough.

• Account number and, if required, a port-out PIN or passcode.
• Billing telephone number (BTN), the main number the account is billed under.
• Service address exactly as the carrier lists it.
• Authorized contact name and the business name on the account.
• The full list of numbers to port, including toll-free numbers and fax lines.
• A signed Letter of Authorization (LOA), when the gaining carrier asks for one.

Plan what happens to every number

Decide where each number lands before you submit the port: a user, an auto attendant or call queue resource account, or a service such as fax. Teams uses user numbers for people and service numbers for resource accounts, so request the right number type for main lines and queues.

If you port only some numbers from an account, the carrier may require the remaining numbers to stay under a new BTN. Porting the BTN itself can close the account. Toll-free numbers usually port on their own track. Settle all of this with the old carrier before you submit.

Submit, confirm and schedule the cutover

Once the port is submitted, the losing and gaining carriers exchange details and agree a firm order commitment (FOC) date. Lead times vary from days for small ports to several weeks for large or complex ones. Build the project timeline around the FOC date, not the day you submit.

Before port day, assign the numbers in Teams, test the call flows, and confirm emergency addresses for each user and site. On the day, test inbound and outbound calls, the main line, every queue and voicemail. Keep the old system ready to take calls until the port is confirmed complete.

Common reasons ports fail or slip

Port problems are predictable, which means most can be avoided with preparation.

• The name, address or BTN on the request does not match the CSR.
• A port-out PIN or freeze is on the account and nobody knew.
• Numbers belong to a reseller or a different account than expected.
• The old service was cancelled early and the numbers were released.
• Hidden numbers, such as alarm lines or fax, were left off the list.

Temporary numbers reduce risk

You can configure and test Teams with temporary numbers while the port is pending. Users get familiar with Teams Phone, call flows are proven, and on port day the real numbers simply replace the temporary ones. This keeps the cutover itself short and predictable.

How Accred Consulting approaches it

Accred Consulting treats porting as part of the voice project, not an afterthought. During discovery we collect the CSR, account details and a full number inventory, decide where each number lands, and flag numbers that need special handling. The US-based specialists on your engagement prepare and track port orders with Microsoft or your operator, schedule cutovers around confirmed FOC dates, and test every main line, queue and user number on port day. Handover documentation records which numbers live where, so your team can manage changes afterward.

Track record: 475+ client projects, 2,000+ migration workstreams and 210,000+ users migrated by a US-based team. Company facts · Case studies

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