Disgusting service from Mercedes Benz Umhlanga

Absolute poor and unconcerened service from the staff at Mercedes Benz Umhlanga. I took my car in for its 2nd annual service on 6 Nov. Exactly 8 working days ago. Nobody had the decency to call me an advise on the status of the simple service. When I called, they advised they wanted to do a system update which would improve fuel efficiency etc which could take up to 3 days. By ny calculation that should have been conplete by 9 Nov. To date no one has called. I have called many times. No answer or when answered, transferred to a dead line. Eventually 2 people promised to call and advise. Nothing this morning, was advised that there was nothibg they could do. I'm really nit sure what my options are. I guess I'm going to go in tomorrow and demand the return of my car. Would you believe, even the complaints department isn't interested.