Worst service!! Garden City Motors

This is the worst service EVER!! My car went in for a problem they phoned to say the car is ready, I asked if they have checked the other problem as well they just said no. I collected my car the afternoon and the problem was still there. I took the car to Tyre Mart just to realize that Mercedes NEVER replaced the faulty part. When we phone them we hold on for 30 min just to get no reply we leave messages for the managers or anyone to phone us back, but still nothing.