OFCA’s number-portability leaflet sets out the important order: the new carrier handles the transfer, and the old service ends when it succeeds. Buying an ordinary new SIM is not the same as selecting “keep my number” or “port in”.
Before submitting the application
- Ask the old provider for the commitment end date, final-bill rules and an early-termination quote. Porting does not erase device instalments or contractual charges.
- Check the registered name and identity document against the new application. Resolve an ownership mismatch before selecting the transfer date.
- Keep the old SIM, account details and any requested SIM serial number/holder certificate. Ask the new carrier which documents its prepaid or postpaid route requires.
Allow for delivery, not only the transfer itself
OFCA describes a normal porting process of one to two days, but that is not a promise that an online order arrives and activates tomorrow. For example, SUN Mobile’s online process sets its earliest effective date 14 days after application to allow SIM delivery. Use the receiving carrier’s confirmed date and avoid scheduling the switch during a flight or a critical payment.
A contract end date and a billing-cycle end date may be different. Ask the old carrier what will be charged for the proposed switch date rather than assuming you can always avoid a full final bill. Save the transfer confirmation and any cancellation deadline supplied by the new carrier.
On the transfer day
- Follow the new carrier’s activation instructions; keep Wi-Fi and another contact method available during the change.
- Test an outgoing call, an incoming call, ordinary SMS and mobile data. An installed eSIM profile alone is not proof that the number moved.
- Check important account messages and keep access to recovery methods. Some services may impose their own security checks after a SIM change.
If the port fails
Contact the receiving carrier with the application reference and exact rejection reason. A name mismatch, inactive old line or incomplete documentation requires a different fix. Keep the old account funded and active while correcting the request; do not cancel it to “force” the transfer. After success, review the old carrier’s final bill and separately end any services that did not transfer.