I had a similar response when I called to have my wound review after my op, four week waiting time! Once I pointed them in the direction of the letter the surgeon sent them instructing them to check the wound and remove dressings at the two week point they booked an appointment for the correct time and date - one must have magically appeared!
FO and Hurtigruten go there, I think Ambassador do as well - not sure about NCL, but the main ones from Southampton, P&O, MSC, Princess, Carnival only do shorter 7 day cruises.