Incorrect deduction by Thrifty and no refund

I offered to pay for my French visitor's car hire. I processed the a portion of the payment online when I first booked the car and swiped my card for the rest upon collection of the vehicle. My payment was a mere generosity. The contract was in her name, and her credit card was used for the deposit. However, my credit card details were stored on their system (without my knowledge), and a fine deducted from my bank account. This is despite have zero contractual relationship with Thrifty, and giving NO authorisation to have that money deducted from my account. So proceeded 3 days of calling and emailing, and someone eventually assisting me. However it has been 2 weeks now, the money has been deducted out of the correct credit card but my refund has still not reflected in my account. I follow up daily and still nothing. These people have essentially ****** money for me. Since I have received no assistance, I will have to lay a claim at the small claims court. Unacceptable really.