Hello, call Carnival or have your agent call if you use one. Also try to get a free upgrade if you are not entitled to a refund. If they cannot refund you they may be willing to upgrade you, this way they lose no money in a sense and you get a better cabin( not that any cabins are bed, I would rather be in a cabin with no window or bed than to be here at work)for your money.
Good luck!! Have a safe and happy cruise!!!!