cargo van rental

I recently rented a cargo van in NH. When I first went to go inspect the first van to rent two employees accompanied me. One was training the other. The one that was getting trained was marking down the dents, scratches, and dings on the vehicle as we walked around it. There were scratches and dents all around the van. When we went to look inside the van we smelled gasoline. So I got in and sure enough there was gas all over the inside of the van. So we went and checked out another van. It too was a mess all over the van with scratches and dents and also protrusions from inside out. After the trainee marked everything down I looked at the picture with all circle, x marks, and three parallel lines to indicate scratches, dents, and dings. I was assuming that she got everything so I agreed that was the condition of the vehicle. When I brought it back there was a third lady who checked me in. She thought she had noticed a new scratch on the van and marked it down. I quickly told her that she was wrong and that I didn't scratch the van. Well sure enough they charged my credit card for damages of $500.00. Oh and another thing when the first truck was in good condition and I had to check out the next one I never signed another authorization slip to charge my credit card in case of an accident. They just printed up a new slip with the same agreement number and different license plate number. So even if I did scratch, which I didn’t, is there any way that is credit fraud because I never authorized that amount, nor did I sign anything for authorization of that vehicle. Any help would be nice.