Depending on who your travel agent booked with, the reservation systems generally consider these type of changes as a cancellation and rebooking. Hence the loss of the credits.
That being said, tell your travel agent to call 1 800 COUPLES and we will ensure that you do not lose your credits. If the issue reaches my desk, I have no problem telling the tour operator the same....
We look forward to welcoming you home again soon.
Chief Romance Officer and Senior Vice President