WhatsApp has Change Number feature which allows you to change phone number related with WhatsApp account on the same phone. The feature is planned to be utilized before you verify your new number. When the WhatsApp Number is change only those you share group chats with will see the new number.
To use the Change Number feature will migrate your account information including picture profile information, groups and settings from your old phone number to your new phone number and also delete the account related with your old phone number.
With this feature, your chat history will still to be available on your phone with the new phone number.
To Start the Change Number Process
=> You must be sure your new phone number can receive SMS or calls and also has an active data connection.
=> You must be sure your old phone number is currently verified in WhatsApp on your phone.
=> To check what number is verified in WhatsApp: Go to WhatsApp => Menu Button => Settings and tap on the Profile Picture.
To Changing Your Phone Number
=> Insert the new SIM card into your device.
=> Open your WhatsApp app.
=> Check if your old phone number is currently verified.
=> Go to WhatsApp => Menu Button => Settings => Account => Change number.
=> Type your old phone number in the top box and also type the your new phone number in the bottom box.
=> Tap on Done at the top of the screen.
=> Now will be prompted to verify your new phone number.
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