Selling accident cars off as clean

I bought an Audi A4 at executive toys last year February and was assured that the vehicle had never been in an accident. The car started to give problems and when taking it in to audi I was told that the vehicle had been in an accident. A transunion search was done which confirmed this, and the accident was significant as the value of the claim was in excess of R80 000. I then informed executive toys and they deny knowing that the vehicle was in an accident. Something I have difficulty believing as they claim to properly check out all their cars. I guy at audi in less than 5 mins and just by looking at the vehicle pointed out numerous things that had been repaired or replaced and NOT even by Audi I might add. Executive toys then agreed to settle the finance on the car plus R10000. On condition we buy a new vehicle from them. We got quotes from Audi and they were to match the price. Till now 3 and half months later I am still waiting, all the while still paying my monthly installments on the vehicle. Being pushed from pillar to post, numerous calls, emails etc. I have now decided to pursue with legal action. I feel so angry at their deceit and unwillingness to take responsibility.