No after sale service

I bought a second hand car. I did not have a lot of money to spare so I was very direct when I said I need something cheap but reliable. I got the 108 point check line that all cars received to ensure quality. Well quality is not what I got. I have left the car at the service department, who also had the car viewed by a separate garage and they still cannot find out what is wrong! The engine bucks while you are driving and you lose power. The is all within 1 1/2 weeks of purchase. I had to propose that they either refund my cost or trade it in for another car. I was told no, we do not do that and if you want to trade it in for another car, then they would buy it back less 10%.
I am calling Mazda Canada.... There is no customer service here....they just want a quick sale and the screw you!! You have a better chance of quality cars on Craigslist!