Complaint Review: Enterprise rental car

we recently rented a car after an accident. When we picked up the car we looked it over, she wrote down some scratched, dents etc but when we pointed out some small marks she said if its smaller than a dime size dont worry about it. Four days later we returned the car, the attendent called us over to show us a mark he had found. We had to get on our knees tp see the incredibly small dent that was no more than dime size and very shallow. The damage was so small that it could have very easily been missed the first run through, it was barely visible even with someone pointing it out. They filled a claim stating that we had damaged the car . We called to file a formal dispute the first person we talked to said that the damage had already been fixed ( a lie) and it would be $750. We asked to see proof that this damage was never reported before, they refused. After about two weeks we called again and spoke to someone else that said after investigation that we were liable and sent us a bill for $1000.  

We did not commit this microscopic damage and now we are expected to pay $1000 dollars. Its unbelievable to me that they can charge their customers for damage they did not commit. They are crooks and something needs ot be done about it.