Play Games Services is a different type of account binding service that links your FFBE account data to your Play Games user activity. For this reason, it is not possible to change binding methods without restarting the FFBE application. If your FFBE account has been bound with another method such as Facebook Sign-in, you will still be able to sign in to your FFBE account using this method. However, please note that PGS must be turned off in order to sign into your account with another binding service.