A trick I have heard of is to walk up to the desk and ask for an exec level room or a suite before you tell them you have any reservations. Since they think you are an off the street customer who will be paying the full rate, they will give you an honest answer. Once they tell you the room is available, give them your reservation number and ask to be upgraded to that room. They will have a hard time denying the rooms are open then, since they just told you they were available.