Mercedes Benz Dealership not refunding cash for parts

I correctly supp**** the salesperson with the VIN number fo rmy car an A180 CDI W ********** model. I needed a carnkshaft pulley. The part was found in Cape Town and I was told it would take 2 days to get to Centurion and would cost +-R2,500. I immediately paid for the part. The part was delivered on time but it was the wrong part. Then when I brought the sample they used the part number and it showed the crankshaft was going to cost +-R5,000. I declined to buy the part and requested a refund. The Salesperson then told me it would take 7 working days for me to be refunded my money. I then went to the Parts Manager who assured me that it would take at most 3 working days to refund my money. It is now 4 working days and I have not received my money or any information from Mercedes Benz Centurion when they will refund my money.