No refund after incorrect debit order deducted.

On the 1st of July 2015 our debit order was deducted for our medical aid as per usual but this time it was a huge shocker as the usual amount was not deducted but instead they deducted R8 835.00 too much. I immediately contacted Discovery whereby I waited on the line for about 20min for the consultant to go speak to her supervisor as I was apparently the 3rd or 4th caller with the same problem. It was discovered that they incorrectly deducted backdated Vitality installments which actually were not even meant for us. They told me that this was the problem and they see it is definetly not for my account. The consultant asked me if I wanted to hold on while she got hold of the Vitality section and informed them to refund me. I opted to wait on the line for her as then I knew for sure it would be sorted out immediately. I was then informed that it would take 5 to 8 working days. I constantly kept in touch with them as I knew the money was not in my account. I had numerous times answered their requests for all sorts of information so that I could get my refund. Today is the 16th day and still no refund. I still have to pay my other acc. but cannot due to no refund yet.