I think I can help! We cruised in April, and also had a cruise for May 2017 already booked prior to the cruise. We went to the desk and were able to "rebook" the 2017 cruise and receive the discount and onboard credit! The gentleman who helped us canceled our existing reservation, then rebooked in the same room. We did have to pay a new deposit though (so be prepared for that) and then the previous deposit was refunded to us within a few business days. We ended up in the same stateroom but with a new confirmation number. Hope this helps!