I'm sorry to hear that you had a bad experience.  I've cruised Carnival for a number of years and found it to be a great experience overall.  Was there a particular aspect that did not go well?  Did you speak to the Hotel Director about your situation and the difficulties you had?  Often when I have a situation that arises, I speak to the staff and ask for some help or guidance in clearing the situation.  If the staff is not able to help I go up to the next level.  Mind you I don't sit back and say nothing... I try to dialogue with the crew to find a positive solution. I will agree that I've had some situation that were more difficult the other, but honestly... they were on the other cruise lines.  For me Carnival was always tops in solving the situation. 

Don't evaluate the whole cruise line on a 4 day cruise... Try a large ship for a 7 day period and I guarantee you will have a better experience... The cruise is what you make of it...