Bungie does not have your personal login information. Bungie does not store your login credentials, nor can Bungie verify your account ownership with anything other than your ability to authenticate to an account. Bungie will not forcefully disable Cross-Save, nor will Bungie forcefully unlink one or more accounts just because you claim they're not yours. The Cooldown for Silver purchase will not be reduced or removed, and once it has been waited out, you'll still need to authenticate to ALL linked accounts in order to disable Cross-Save. Again, if you cannot authenticate to them, then, unfortunately, your Cross-Save will remain as it is.