A phone number already being used with the WhatsApp Business API cannot be migrated. You will have to pick a different phone number.
You can use a phone number that is already registered in the Android, iPhone, or Business Application versions of WhatsApp. However, if you try to add that phone number to your Business Manager, you will see a Phone Number Is Invalid error. You will need to follow the below steps to delete the WhatsApp account associated with that phone number. Any incoming messages during this time will be queued by the WhatsApp servers and delivered upon successful registration.
- Open the WhatsApp (or WhatsApp Business) Application on your Android or iPhone.
- Navigate to the Settings page.
- Select Account.Account Settings
- Select Delete my account.Delete My Account
- Follow the steps to delete the WhatsApp account for that phone number.Deletion Steps
Once you complete the above steps, go to your Business Manager to add the phone number and complete the registration process.