See the casino host next time. The rules are posted at their desk. Also, you do not have to sit down with anyone, you can just fill out the form on the back of the flyer at the casino host desk and they will charge the deposit, and you have 7 days to make a reservation. They are clear that there is limited availability, and unfortunately with the reduction in points for free cabins over the last 6 months, there were way too many cabins handed out for players that would not normally have gotten one. That is why you are having a hard time finding availability.
I don't like the new program, but it is all spelled out, so not much I can do about it. Good luck!