If you changed your phone number and kept your same iPhone, you can change your number within WhatsApp. Before proceeding, make sure that your new number is activated on your phone and that you can receive SMS messages and phone calls.
This process will:
Please follow these steps to change your account phone number:
After successfully verifying your new number, your old account information will be migrated to your new number. Please make sure your WhatsApp contacts have your new phone number saved in their phones' address books to ensure a seamless messaging experience.
WhatsApp Support Team