Once created a linking to Facebook/Google/Game Center can't be deleted/changed by a player.

 

What we can do for you is to delete the linking. All such requests are being looked into with the maximum thoroughness as a part of our security measures. We can ask you for additional information to identify you as the game account's owner during the process.

 

If you wish to continue please raise a ticket via in-game settings (Settings - Support). The ticket must be created from the game account which you wish to unlink.