Non - Refund of Deposit

I rented a vehicle from Europcar from 17th - 20th October. On return, I was told that all was ok, and that I could leave. I was promised a refund on my deposit within 3 - 4 working days. 10 minutes later, I was called back to say that there was a burn on the passenger seat. We are not smokers, and I did not notice the burn when we took delivery of the car, as I was excited to begin my holiday. I was then asked to complete and incident form, when I advised that the burn on the passenger seat had to have been there when we took delivery of the car... I also advised the gentleman doing the check on the car that the car actually had a very strong smoke smell when we took delivery, but we were in a rush to fetch my child who lives in Cape Town, and we were eager to get on with our holiday... Since then, I have queried about the refund of my deposit on several occasions and have not heard back from Customer Services. I refuse to take responsibility for something that I am not at fault for! Also, looking at all the complaints on Hello Peter now, and the standard response that Calvin May types, leaves a lot to be desired, as it seems many people are being ****** of their deposits!