ARE OUR CONDO RENTAL RESERVATIONS GUARANTEED

Our Florida Condo has it's own Sales & Rental Office. The rental manager gave a guest last March, 2010 a reservation for which he laid money down on for a rental Jan. through March of 2011. It was a Sheet showing the total rate, with Reservation #, very professional like all guests get here. This past Nov., the guest received a call from the rental office, asking him if he and his wife would consider moving to another unit, when they arrived. Reason being, someone else wanted to rent that same unit for a longer period of time. The Guest said, no, they did not want to give up their reservation for that particular unit, and he asked for a letter from the rental manager to confirm that conversation. 5 days later he received that letter, affirming he would not get "bumped" to another unit, along with the Reservation Page, showing total rate, period of time, reservation #, etc. Upon arrival, the guest went to pay for 1 months worth of that rent, and all of a sudden the total rate had gone up $1,600. I know for true fact, there was no rate hike from 2010 to 2011. Furthermore, the Manager looked at the Guest and said, "surely you should have known it couldn't have been for the rate we sent you?" And furthermore went on to say that if he didn't pay the higher cost, they would be asked to leave. FYI - These are the dearest people in the world. I though reservations quoted and sent out for guaranteed for rate and availability, amy I correct? Can't find this info on the internet.