I have had an experience similar to this 18 months ago in Duesseldorf. Rented the car for a week, returning it to the small station on the outskirts of town. Took videos and photos of vehicle, odometer, fuel reading etc.

Then got an email saying I owed them the best part of EUR1000. It wasn't until I really chased them down requesting photos of the vehicle that I noticed they were trying to charge me for damage to a BMW.

We had C class