Bad customer service

I recently bought a used vehicle at this dealership they claimed they did a Valet on the vehicle of which is not true there are bad polish marks on the vehicle cars Aircon doesn't work they claim it was working before it left the dealership its been a month now and almost everyday I discover problems with the vehicle they claim they did an inspection of which I doubt they did car had no oil when I left the dealership I had to put 3 pints of oil, when I call them I can see they trying to shift blame on me.