Multi Franchise selling faulty car and refuse to refund my money

they sold the faulty car to me, which they knew the car has a major problem. and they can not fix the car but they refuse to replace with the new car or refund my money . i bought the car with finance and paid 3 installment ,they don't want to refund my installment. i bought in December 2020and car was in workshop from Jan. after 3 months which they couldn't fix the car they don't want to pay my money back because i drove 3000 km with car. i bought from Durban branch. the car is Renault kolos 2020 demo model. people please avoid multi fransice and Renault sa they don't care about the customer. if i could i didnt give any star .