Damage?

In June, 2013 I had spent a grueling day of travel with my elderly mother.  I had reserved a rental car with a competitor company but realized that that company was off the premises. By the way we were in Orlando MCO.  One of EZ's company representatives flagged me down and said that they had cars available on the premises.  So unfortunately this is when the nightmare begins.  Their location is in a shady area of the airport and very very dark.  They asked us to look at the vehicle closely.  First of all, we couldn't see the vehicle very well because it was so dark.  We drove about 40 minutes to visit my brother.  The car sat in his driveway for 5 days.  I only drove it to the grocery store one time and then back to the airport.  They claim that I damaged the vehicle on the hood of the vehicle.  Like a rock hit it and dented it or something.  Well I can assure you that if that would have happened when I was driving the car I definitely would have noticed.  I am more than willing to pay for any damage that I caused but this is pure bull.  I did NOT damage this vehicle and they are now harassing me and trying to get $500 out of me.  The latest is a letter saying that if I will just pay half they will be okay with that!  I am not willing to give them one red cent!  They are scammers and should be ashamed of themselves!!!!!!!!!!!