Disputing the charges will get the ball rolling very fast. Depending on who paid for the rooms some of your guest might not be willing to go through the process of a dispute/charge-back.

I had problem with some hotel stays. When there was no reply from hotel management or the chain I instigated a charge-back for the full amount and there were either immediate resolutions or the charge-backs were not disputed.

Also leave comment about the hotel on trip-advisor and other travel feedback sites.