Appalling service!!

I've had a very terrible ordeal with Mercedes Benz (Sandton). Second Merc i'm driving and every time i take my car to them it comes back with scratches or further mechanical faults. It's gotten worse since they moved to the new building. Now my car , which is only under a year old takes off only at gear number two. They tell me this is normal and yet I have two cars same model and they don't behave the same as they claim. The centre manager doesn't even have the proper business etiquette to deal with clients! I'm so appalled. But not leaving this one lying down!!!