Car broke down with a month after purchase.

My brother in-law purchased a car from we buy cars Port Elizabeth on the 22/12/2022 Renault duster 1.6 expression 2018 year model. The first installment was supposed to be on the 30/01/2023. Friday 13/01/2023 the car was not starting, he then called his insurance to tow it to we buy cars in Port Elizabeth. They promised that the car will be ready on Monday, they went back to find the car in the same condition, they couldn't find any tangible answer as what is wrong in a car, they were not given a choice on getting another car since this car is still new, it haven't finish a month with us. They asked to speak to the manager and they waited since they said he was busy they spent 4 hours, they left around 5:pm . They were asked to come back tomorrow but they have decided to take matter to this level because of the store service. There's still installment to be paid at the end of the month.