Unlinking Your Game Center/Google Play Account
Go to Menu > Account Transfer > Unlink.
This will unlink your Game Center/Google Play account from the game account.
Resetting Transfer ID and Password
You can reset your Transfer ID and password by setting up account transfer again.
Your old Transfer ID and password will become invalid.
1. Go to Menu > Account Transfer > Transfer to different OS.
2. Choose a new password and tap "Set Password."
3. A new password confirmation message will pop up. Tap "OK."