Very unhappy customer(Car care clinic)

I'm very unhappy with their service. I took my car to them for a service. They had a special for a full service for R1800. They phoned me and told me my car was leaking oil and mentioned a few other problems on the vehicle. My car never had any oil leaks before I took it to them. I told them to fix it while it was there. At the end of the day I ended up paying R3500. And now my car is leaking oil and every now and then lets out smoke. It's seems like that is how they make money out of people by having a "special" and then they add a lot of extras to milk more money out of you, and now my car has more problems after I got it back. They will never see me again.