Pathetic service for a premium brand

It has been a week since my car was sent to the dealership following a complete breakdown the night before. This happened after servicing less than two months before the breakdown. Requests to both the workshop manager, Wayne and the service advisor, Mandlenkosi for diagnostic testing went ignored for days. Instead I was presented with an quote for what I was told was a compression problem. When I asked how they determined this was the problem, Mandlenkosi could not answer me. I asked for the diagnostic test result again both telephonically and by email. At that point all communication from their side stopped. So I have a 13k quote for assessment repairs which I am not certain is really the issue, and likely to be charged more. Audi Sandton is no longer communicating with me by phone or mail but still have my car. A complaint to Audi SA sent two days ago has been acknowledged as received yet no one has responded to me either! Beyond disgusting. Next steps...