Can you get a refund for your cruise over a dirty balcony?

If you find heavy soot on the balcony of your cabin, should you be able to leave the cruise and get a refund? Rafael Rottiers and his wife believe so. They insist the filth on the railings and floor of their cabin’s balcony aboard Costa’s neoRiviera endangered their health. So they abandoned the ship days before it ended.

Now that the couple is back home, they want a refund. But what exactly was that document the two signed before leaving the cruise?