How to Fix 'Phone Number Is Not Registered' on a New iPhone 18

The message means WhatsApp has not completed registration for the number on this installation. Start by checking the country selection and the full mobile number, then make sure the SIM or eSIM that receives the verification message can receive service.

Complete registration carefully

Enter the number in the country format requested by WhatsApp.
Check mobile signal and temporarily turn off settings that block SMS or calls.
Wait for the in-app timer before requesting another code. Repeated attempts can delay the next request.
If WhatsApp offers a call verification method, use it only for the same number.

When to escalate

Contact the mobile carrier if verification messages or calls do not arrive, and contact WhatsApp support if the correct number keeps showing the same state. Do not reinstall the app repeatedly or change the account number as a shortcut; neither action proves the number is registered.

If you need a separate computer-based WhatsApp transfer or backup workflow after registration is complete, Dr.Fone - WhatsApp Transfer provides a dedicated option for WhatsApp data.