After 1 week of back and forth it has been credited. It was very difficult since I misplaced the gas recipt and had to get my credit card company to pull copy,etc and the customer service at Sixt did not seem very sorry. The thing that bothers me the most was that the check in guy took FOREVER to look at every inch of the car, inside and out and I waited for 10 minutes and still could not get final invoice. I guess in the future returning to FRA I will use Hertz