Extremely poor service from Automania in Midrand

I bought a Porsche Cayenne, used car at Automania in Midrand. When I was driving the car out of the car dealer it reported that the right back tyre is inflated, and I didn’t know what that means. I balanced the tyre but the problem insisted. I then got it checked, and a scary discovery of misaligned tyre shocked my life, on top of that there was a patch on the same tyre and a nail. I had to patch it because I could not buy a new tyre. After two months when I was registering the car on my name, it required roadworthy test. I took it for roadworthy test and it failed due to tyres that were not in a good condition and I was advised to buy new sets of tires. I was shocked because I have been driving the car for 2 months. I called Gareth from Automania who was my salesman and explained everything. He told Automania cannot assist me with tyres because with them 2 months ago the car passed roadworthy test in Midrand. So I had to buy all 4 tyres in order for the car to pass roadworthy, and I spent about R12000.00, which I believe is the costs that were suppose to be incurred by Automania before they sold the car. I feel they took advantage of me by not changing tyres and am sure the inflating tyre notification was there and they saw it but decided to do nothing about. I want my full refund from Automania.