Unbind the phone in the mile.

Since mobile phone A is bound, you can enter it as an account name, enter the account name of the mobile phone, click Forgot Password, reset the password through the information sent to the bound mobile phone, then find a mobile phone number that has never been registered (which can be a new friend's) to change the binding, let your mobile phone A log off, and finally log in to the account of mobile phone B to change the binding of mobile phone A..