Changing a Character's Last Name
To change your character's current last name to a new one, target yourself and type /surname (new last name). After using this command you may not use it again for 7 days.
If you prefer to remove your character's surname altogether, just type /surname and hit the "Enter" key on your keyboard without typing anything else. Anything you type after the /surname command will be interpreted as a surname request, even if that wasn't your intention. Please note that you will still need to be clear of the 7 day limitation to remove a surname.