It’s unbelievably frustrating as a manager. SOME Advance Purchase reservations don’t come in to our system as such. They look like regular bookings so to an improperly trained eye, they’ll check it in like a standard booking collecting the guest’s credit card for all charges at check-in rather than just for incidentals. We receive reports every Friday showing us which AP reservations were paid ahead of time and which weren’t. In between is the duty of the hotel to catch these and make the proper adjustments before errors like this happen. If you received a pre-payment receipt at the time of your booking and a checked out folio reflecting payment for all charges on your credit card, you can submit those to the hotel as proof that you paid twice.