The change number feature allows you to change the phone number associated with your WhatsApp account. Changing your phone number in WhatsApp will:
You can choose whether you want your contacts to be notified about your phone number change. Your group chats will be notified when you change your phone number regardless of whether you choose to notify your contacts. To stay connected with your contacts, we recommend you inform them about your new phone number before changing phone numbers and ask them to make any necessary changes in their phones’ address books.
Note: If you change your phone number and continue using the same phone for the new phone number, your chat history will continue to be available on your phone.