I had several small charges that were inconsistent with what I spent, but after an hour in line at guest relations, they simply said "well it is what we have documented". I gave up as it was minor but I did think it was poor customer service. I understand the concept of principle!
It would also be helpful to know that if you forget to get your charges before you leave the ship that it is next to impossible to get them later at least in a timely manner. Our cruise was a disaster for everyone, so handling things with guest services was a several hour experience. I completely own that I did not get a print out before I left, but I didn't know how hard it would be. My mother was injured and I needed to send information to HAL's insurance within 7 days. I have sent emails, called, and tried on line. I have long since missed the window.
SO be sure to get your statement before you get off the ship!!