The very first time I cruised, I prebooked a massage for myself and husband and paid in full. Once on board we received our massages, but were charged again. This was not acceptable as we had already paid for the service. We had to go Guest Services, who at first said it would take up to 10 days to have the credit returned. That was also unacceptable, I bought out my receipt that showed they were paid in full and asked to speak to someone higher up. The charge was taken off our SS account. But having to stand in line and deal with this problem is not why I prepaid
We no longer prepay and find very nice deals once on board.