Cartrawler 5 weeks later and no refund??!!

I hired a car through Cartrawler's website, when I arrived at the airport to collect my car the supplier would not accept my credit card as it did not have raised numbers and is a local card. Nowhere on their website or terms and conditions is this mentioned. I called on Monday 5th October to request a refund. I was assured the matter would be looked into but when I called 2 weeks later nothing had been done. They then asked for additional information which I supp****. 37 days/ 5 weeks later I am still waiting for my refund. I can now not get through to the call centre and have been trying for days. I have heard nothing from them at all and even though their website promises a 20 day resolution that seems to be a lie along with their promise to refund me.