I'm so very sorry for your medical problems and hope that you will be able to cruise again in the future.
Having said that, and it sounds like your experience with customer service was horrible, I actually had a good experience yesterday. We each bought two future cruise credits when we were on a cruise over last Christmas. One of them is being used for a cruise next July. Our accounts didn't show the other one so I called about it. We went on a cruise last month and for some reason I thought we had booked it before our cruise last December when we bought the credits so I called to ask about them. The girl was very helpful and I was wrong - we used them for our last cruise. Anyway...she was very professional and helpful so maybe it depends on who you get. Also...I was happy to see that I could get an answer on a Sunday.