Bogus Charge

Having hired a car previously from LOCAUTO, I vowed never again, however I was unaware until I printed off the voucher just before travelling that the company I had booked through was a booking only company, It was too late as I had already paid and ended up after an extremely long wait (again) ended up with a Fiat 500 from LOCAUTO. Having returned the car in good condition with  full tank, I was assured that everything was ok and there would be no additional charges. Now over 3 months late this company has taken £35 from my credit card. I want to know why and I demand a refund. Avoid this company