I would like to warn you for Sixt in Frankfurt. When we returned the car we checked the outside of the car with their staff to make sure there were no extra damages since we rented it in the morning with some damages/scratches. However, some days later we receive an invoice for 850 EURO for damage that occured during the rental period according to Sixt. Of course, we have no proof, you do not take photos of an undamaged car. Moreover, they do not reply to our letters and complaints, they keep sending the same standard answer with some photos, they excuse themselves for the bad quality of the photos :) but will not contact the person who checked the car with us in Frankfurt upon returning. No more car rentals from Sixt for us, because there is no way to avoid this kind of problem.
Anybody else with the same problem?