Rentalcars.com refusing to refund for services NOT rendered

On Tuesday, 15 March, I app**** to rent a car from Rentalcars.com (Reference number 726 222 163) at around 7am before getting on a flight from East London, South Africa to Johannesburg. I paid an amount of R3 213,90 to Rentalcars.com which included the rental amount and full comprehensive cover for the rental vehicle. I arrived at the OR Thambo airport at around 11am the same day and went to Europcar to fetch my vehicle. I was asked to pay a deposit of R7 999 for the vehicle, but when I wanted to pay using my debit card I was told that I needed to have a credit card. I do not have a credit card and therefore could not take the car. After not being able to take the car I contacted Rentalcars.com to request the money back for the services that were not rendered through them, but was told I was not able to get this back as I did not cancel the request. I had absolutely no intention to cancel the rental request as I was never told that I needed a credit card to rent the vehicle. As soon as I was aware of the issue I contacted them to ask for the money back and have had no success in the matter. I feel that the fact that I do not have a credit card has infringed on my ability to get a rental car, and that Rentalcars.com has made absolutely no effort to refund the money they received with open arms, but gave me no service in return.