Billing issues and bad after care service

I am a very disappointed customer with this establishment. I took my car in for a service in January and was quoted a certain amount for the service rendered and a part for the service. .I have no problem with the paying what I was supposed to. But upon going back to the store to pay for the extra service rendered for putting in the faulty part the lady accidentally charged me for the full service and part in stead of just for the secondary service. What I have a problem with is that it now more than two weeks later and I was told my refund would be processed as soon as thier bank released it on thier side. I have been up and down to my bank to get proof of this payment problem and faxed it to Dirk Ellis Motors in Jeffrey Bay but I still have not received my money back. I am upset and disappointed that this could not have been resolved earlier. I am still waiting a response from this VW dealership.