very upset with this hotel!! I booked a conference...

very upset with this hotel!! I booked a conference with this hotel and booked my room. The hotel overbooked the conference room therefore the conference was canceled and they are refusing to refund my room.. I did buy a non refundable ticket.. but I DID NOT change my mind.. this was a hotel error and now it is costing me an additional $50 to change it.. furious!! Never again Hilton!