Rental cars

Few years ago we rented a car at the air port. When we returned it a week later, the rep put his hand under the engine area and had a little oil on his fingers. He said I would have to pay $150 to repair the problem. When I got back to our hotel, I notified AMEX. I was told when I got back home to send them a copy of the bill. Since the company would not verify the bill, my AMEX card was rembersed for the charge. We have not rented a car since because it is a lot cheaper doing a taxi- the only reason we rented then was to take a 3 day trip to Patazuaro(what a wonderful little city to visit).