Unsatisfactory car deal

We bought a car at We buy cars with platinum status as for their sale i.e. the car without anything wrong with it ,they didn't reveal the defects of the vehicle which they were supposed to inform us of, eg the car is mechanically sound and having any other problems and ifit had been involved in the accident before or not. The total amount of R156.5k paid incash to the dealer. We only found out when we were driving it home that the car was a s****.we phoned them they told us to come with it . when we get there they told us to take the car to their mechanic of which he wrote lot of things faulty with the car. Now the problem is we don't want the car they refusing to take it back and refuse to return the money so that we could go and buy the car somewhere else. Our sales person name was James from Springfield branch Kzn province. The buyer of the car is a pensioner and was using his hard earned money from his pension fund looking for a reliable car but it is his heart breaking. He has a dimensional chronic sickness. He doesn't want it anymore and wants his money. The dealer staff were not of any assistance please assist