Last summer I needed to move a prepaid room reservation back by one night.
I am a Diamond member and that didn't get me any assistance.
What finally enabled me to move my reservation, was that it then fell fully over the weekend, instead of tying up a room at a sold out business property on a Thursday night. The hotel manager had to sign off on it. She admitted that she only did it because it helped her.
I think I was very, very, very lucky to be able to move my reservation. They made it clear that was a major exception to their policy.