Tempest Car Hire- charging for fuel when the tank was already filled up

Was disappointed to receive my invoice only to discover that I had been charged for both a fuel refill and a fuel refill surcharge. I had actually filled up their hire car at the BP Garage situated at the airport a few minutes before handing back the vehicle. I called them after I received the invoice and luckily I had taken a photo of both the odometer and the fuel tank. I was asked to submit the photo to the CT branch and since then, I have had no reply despite a follow up e mail. My credit card remains debited with the additional amounts. Not happy with their lack of response and feel cheated by a service provider that I normally always choose before anyone else