Please follow these steps to change account phone number in WhatsApp
Make sure new phone number can receive SMS or calls
Open WhatsApp
Press Menu Button
Make sure new phone number can receive SMS or calls
Open WhatsApp
Press Menu Button
Press Settings
Press Account
Press Change number
Press NEXT
Enter old and new phone number along with country code and Press DONE
Enter verification code received by SMS/call
You will get confirmation message, Press OK