I do understand the frustration. I had to change a Moorea reservation as well. I tried once and they transferred me to the hotel (who then put me on hold and then never answered). All I was trying to do was upgrade my room category (in other words give them more money for the same dates). I gave up and then a couple of days later booked a second reservation in the room category I wanted and called Hilton to cancel the old reservation. I'm not sure why Moorea requires this but it is annoying since I booked everything through the Hilton website/app.