Require the hotel to facilitate all logistics and absorb all costs associated with the room change, such as signage and audio-visual equipment. It also may be appropriate to ask for additional monetary compensation or concessions, such as a complimentary coffee break, for the inconvenience and confusion that such a situation can create. Ideally, the specific room should have been listed in your contract. Double-booking situations usually occur when the facility has not communicated with you fully. Discrepancies may be caught when reviewing this paperwork, thereby avoiding potential problems after the meeting has started.
Room is set to max.
If an adjoining room isn't being used, open the airwall between the two rooms. If a session in an adjoining room has a low turnout, move that session to a smaller room and open the airwall between the two rooms. If your general session room is unoccupied, relocate the entire overflowing session. If none of these options is possible, offer to repeat the session later in the day or later in the conference. You should have required delegates to preregister for specific sessions, which would have given you far more control over the number of people in each room.