Number porting
Number porting is moving an existing phone number from one carrier or service provider to another, so the business keeps the same number when it changes provider.
Also called: phone number porting, local number portability, porting a number
The new provider submits a port request with proof the number belongs to the customer, typically a recent bill and the account details held by the current carrier. The losing carrier verifies the request, the number’s routing in the PSTN is updated, and calls start arriving at the new service. Until the port completes, the number keeps working on the old carrier.
Porting is regulated in most countries (in the US under the FCC’s local number portability rules) so that a carrier cannot refuse to release a number the customer owns. The usual failure is a mismatch between the details on the request and the details on the old account.
The alternative to porting is call forwarding, which leaves the number where it is and sends calls onward.