[Resolved] National Car Rental — charging me for damage I know nothing about

I was on a business trip in Charleston, SC last month and got a National rental car at the airport, based on best price.

I didn't immediately check it out thoroughly because I was expecting to be met by a rep on the way out to go over the car. However, nobody stopped me and by the time I realized nobody would be checking out the car I was on main road. It wasn't really until I stopped and looked around did I realize that the car had not been cleaned at all inside or out -- there was trash on the floor and the cupholders were sticky. I was already quite far from the airport and since I was supposed to be meeting someone soon I decided I didn't have time to go back, return the car, and wait for it to be cleaned. I called National at some time during my stay to inform them that car hadn't been cleaned.

When I returned the car, somebody met me to go over it. Amidst the dirt, there was a slight surface scratch/scuff mark but I informed the person that it was probably there already because nobody checked out the car when I picked it up. I know I didn't scratch it or was involved in any bumps or collisions. Nothing was said to me or written on my rental agreement when I went to the desk to settle the bill.

The other day, a month later, I received a letter from the National damage recovery department saying they had received a report of damage and that I was liable, so I need to inform my insurance company or credit card. They did not say what the damage was or how much it was. I tried to call this department yesterday and after going through several layers of voice menus, was told they were unable to take my call because of the high volume of calls, and to leave a message. I did, but didn't receive a call back. I then called National customer service. They looked up my rental agreement and verified that there were no notations on it. They told me I would have to call the damage recovery department to find out what it was about. I asked them, if I had done some damage, shouldn't that be notated on the contract? She said that she doesn't/cannot see that information and it would have been forwarded to the damage recovery department. I ended up writing the recovery department a letter telling them I have no idea what they are talking about because I returned the car in the condition I had received it and had not been informed of any damage.

Last night, I received a letter from a "billing service" company telling me that "due to their sheer volume of claims" National Car Rental has asked them to partner with them in the processing of this claim. Apparently I owe $478.39. For what, I don't know. I now have to write THEM a letter within 30 days to dispute this claim.

Is there any way they can have a claim against me when they never informed me that I did any damage?

I can see this being a long drawn out process of me having to keep writing letters defending against something I didn't do.