Undisclosed mechanical damages

I recently bought a car cash and it started overheating withing 3 days of use. The Derka report did not say anything about it or any damage related to that. I contacted them and they requested a mechanics report, which i sent and paid for including the diagnostic, storage. the company comes back and tells me they will pay a certain amount only for me to do repairs on my won accord . I have told them I need a refund or to pick another vehicle, but they are refusing. sending me from pillar to post. I have paid 2 insurance premiums for this vehicle which I'm not driving, and also currently paying for storage. as the vehicle was bought ion Durban and I work and stay 400kms away.