bought an accident vehicle without disclosure

I bought a car at Kia Sandton in May, three weeks into driving the car I had to take it to roadworthy test to get the necessary registration for my car. At the COR place, an oil leak was found, asked the dealer where to fix it. He said I should book it at the nearest dealer. Did exactly that. The technicians call me to ask me if the car was in an accident,I asked the dealer who sold me the car he says he has no knowledge of the car being involved in an accident. However, after expert opinion the car was indeed in a front smash and anyone with experience with cars would know at first glance. Spoke to the manager about returning the car they refused, they can only take it back through trade in. Very bad business, how do you sell a defective vehicle? This is unacceptable behavior, the manager is very rude too.