Mercedes Benz Rosebank terrible service

I booked my car in to Mercedes Benz Rosebank for a fault (left cornering light - problem with control unit) which occurred for the third time. The first two times I booked the vehicle in for the same problem was in April and May 2017. At my booking on 18 Dec 2017 I specifically gave the history of the fault and what was done before, at the end of the day I was told that my vehicle would not be ready and that I can collect it the next day. I went in 19 Dec 2017 and the vehicle was still not ready since they did not have the part needed to fix the problem. I anyway collected my car only to get home to see that there were severe scratches all over the vehicle caused at the wash bay. I drove straight back to the dealership and showed this to the manager Marco. He assured me that when I brought the vehicle back to fix the light, the scratches would also be fixed at Renew-it. I received a call to bring my vehicle in on 3 Jan when the light and scratches would be fixed - when I arrived there this morning, my vehicle was not even booked in. Marco and Bianca the service advisor had nothing to say to this. The service I have experienced from Mercedes Benz Rosebank has been nothing short of **********. I was assured that my vehicle would be ready this afternoon with everything resolved however I do not have very high hopes of this. I will never use Mercedes Benz Rosebank after this level of incompetence and poor service that I have experienced. I have always owned a Mercedes Benz and do not expect such shoddy service from such a premium brand. I am very disappointed.