The price drop happened to me on an upcoming MSC cruise. I haven't made the final payment yet. I talked to my travel agent, and she said I would have to cancel the actual booking and rebook it. I did this and got the new price. In your case you would have to cancel and repay full price of cruise and wait for refund on existing booking. I only had to pay a new deposit. I always book balcony guarantee so don't care about the location of the room. As long as I am on the ship it is the same experience. I think if you are not picky about what rooms are available after you cancel you can get the new price. Just have to understand that you may not get same category or room.
