Terrible Service, selling defective vehicles.

Disgusting service received from Hyundai Sherwood. Purchased a demo H100 from them with 197kms on 3rd October. They sold me a defective vehicle which was emitting black smoke, with a funny noise coming from the engine. Returned the vehicle to them asking for an immediate cancellation of contract or a replacement vehicle. 3 weeks later they are still "awaiting feedback" from Hyundai South Africa, while I am still liable for insurance and the instalment while not being in possession of a vehicle. Absolutely disappointing for such a big dealership