no deposit refund and poor emails

After 3 weeks since returning my car back to Europcar at Heathrow I still have not received my deposit refund. I was informed that there is no additional damage and the refund would be made automatically after deduction for the petrol- the tank wasn't full. I was also told that there would be a final statement emailed to me ASAP. This hasn't happened. I have so far sent 3 emails and received 3 replies, apparently from a service centre NOT in the UK.On each occasion they say that the UK customer services dept. is dealing with it. They are very quick to take your money and seeminly very slow to refund it, if ever!!!
i am truly disgusted with this company.