They didn't do anything to screw you. The rule of one name remaining has always been the case. With other lines as well. Your thought they want the cabin to sell at a higher price is a figment of your angry mind.
Cancel all, you are of no attitude to go on any cruise now.
Put your sign out in front of your business. If Carnival was a really nasty company, they'd soon own your business. But they will ignore your threat, or action.