Changing your booking is a sore spot with the cruise lines.
The cruising public is very fickle - or confused, or something. It is quite amazing how often cruisers change cruise lines, ships, dates, itineraries, staterooms, decks, categories, and total passenger numbers.
On average, every stateroom is sold 8 times for every cruise before the final occupants actually move in.
Can you imagine the challenges with a ship that has 2,500 cabins?
Having to sell 20,000 cabins just to fill one ship for one 7 day cruise?
Next time you telephone your cruise line and have to wait for assistance, at least you will better understand what all those call center employees are doing instead of helping you.