Billed me for damage I did not cause

Terrible (x1000) service from First Car Rental and this was the final straw since there have been other bad occurrences. First Car decided to bill me for damages on the rental I returned that MUST have been there previously. The damage referred to was scratches on the driver side of the rims. First of all almost R2000 damage is totally ridiculous and secondly it did not occur when I rented the vehicle and obviously was not picked up during the initial inspection. I know I did sign for it but how can they expect from me to scrutinize the entire car?? The scratches were caused by someone else and now they are using me as a scapegoat. Please think twice before renting from First Car Rental, I most definitely will not use them ever again and I am a frequent traveler. BLATANT THEFT AND INCOMPTENCE!!!