What to do if you receive an error message when attempting to connect your Xbox account to your Battle.net account.
How to unlink a Steam, Playstation Network, Xbox Live, or Nintendo Switch account from a Battle.net account
What to do if you receive an error when linking your Xbox Account to your Battle.net Account.
How to move a Diablo III account off a Battle.net account
Information on logging into the Battle.net application on more than one computer
Information on the deletion, transfer, unlinking, or moving accounts.
Link to the EULA which contains the answer to this question.
How to delete your Activision account
How to swap email addresses between two accounts