I had this situation for Andaz Papagayo a month ago.

I called a month in advance and was told that three nights at the new rate would be more expensive than four nights at the original rate.

When I checked in, I told the front desk that I was planning to only stay three nights. They didn't offer to change the reservation and I didn't really press the issue.

In the end, I paid for the four nights and checked out after the third night. I only got three EQNs oddly.