Wrong parts given and money not refunded

I called Mercedes Benz Bryanston on the 2 November to request a replacement grill to be ordered.. The parts rep requested my VIN number to confirm the order of the correct grill and ordered the part accordingly.. I collected it the same day and fitted it later that day, upon fitting I found that the grill was the incorrect size for my car.. I returned to Mercedes Benz the next day with the grill and receipt to request a refund, the parts rep checked the grill and asked for my banking details which I then provided.. He advised that a refund would take between 3 to 5 business working days, this was advised the morning of the 3 November 2015, he took the grill from me and the receipt and gave me no reference for the transaction.. Today it's a week later (10 November 2015) and I've had no feedback, I tried calling into the parts department but got cut off every attempt.. The amount owing is R5000 which I can't ignore..