overcharged

I rented and returned a Europcar at Frankfurt Airport (Germany) in April 2012.  The pick-up experience was great with a very helpful and friendly agent. However, after dropping off the car and receiving the bill in the mail when back in the United States, I noticed an overcharge of $460 for 1500 km I never drove and the check-in location was noted as Stuttgart Airport (where I never was).  After complaining by fax, letter, and through their customer email, the full overcharged amount was credited back to my CC.  Personally, I thought they try to play these games and probably often get away with it.  I can only recommend to demand you final bill immediately after returning the car