My BMW 320d was involved in an accident i was not informed about it

I bought my BMW 320d at Autobahn in Isando, I signed all the papers for the vehicle. I was informed that the car was never involved in an accident. Two weeks later when i took my car to a car wash I realized that the car front left door painting looked different to the rest of the car. I subsequently called BMW Isando, The manager then informed me that it was my responsibility to have checked the car for damages. I trusted them, I am very disappointed about the service.

I took my car today to the panelbeaters which they checked my car for damages, They did confirm that my car was involved in an accident. I also found out the front fender and the side spoiler was also repaired. I just need BMW to fix my car. I sent them the quotation from the panel beaters.