Non disclosure of car being in an accident

We purchased a car at paarlberg BMW about 20 months ago. 3 months ago I wanted to trade in the BMW X5. I got a quote at paarlberg and also from another dealer. The paarlberg trade in price was much higher than the other dealership. When I enquired why the other dealership informed me that the car was in 96k accident as per a comment on their system. When I informed the GM at paarlberg he sent me a\without prejudice"letter informing me that the car was out of motor plan and a non approved bmw. However he did not answer me on why I was not informed that the car was in a R96000 accident. This is non disclosure of a material fact and I want the deal canceled. BMW South Africa says they can do nothing and I must sort it out with the dealership. I bought 3 cars at this dealership in the last 2 years and this is how they treat me? Paarlberg you give the industry a bad name. Prof Peters """