BMW Constantia holding my funds

I was interested in a vehicle advertised by BWM Constantia, I was asked to pay R5000 deposit to reserve it which I paid. When I enquired later I found out the vehicle was long sold. I then asked for my deposit back, I was told I should provide my bank account details and copy of ID and I provided those immediately but the refund was not done. I made a follow up and that also didn't do the trick I still don't have my money. I agreed to pay the deposit because I know BWM to be a big and reputable international brand that is run professionally, I didn't think I would have a problem should I need my deposit back, because I trusted the BMW brand. However I have now been deprived of my money and what I could have used it for because BMW Constantia just won't pay it back and I don't know for what good reason. I didn't imagine dealing with BMW would result in such stress and strife, I didn't think I would have to beg and plead just to get what belongs to me. This is not the kind of service I expect from such a big brand. I want BMW to pay me back my money ASAP!