Has anyone else experienced the con of being advised that gratuities up-front payment was mandatory, but with on-board adjustment available if service was below (or indeed above) expectations - only to find when on-board the rules have changed? My wife & I booked with Carnival USA to go from Barbados in March. The numerous examples of poor service caused us to want to reduce the gratuities to zero, yet we were unable to - this despite having an email at the time of booking which said we could. Protests both on-board and subsequently in numerous letters, emails & phone calls have resulted in bland unhelpful replies from Carnival. How can they take $70 each from us, confirm we could remove/reduce it if required (in writing) & then change the rules? All they offered was a small reduction on our next Carnival cruise - that's a cruise which we'll never go on - once is enough.