Overheating car within a month

Hi

My mother in law bought a car at Kia Fourways on the 27/11/2019. Model (Accent 1.6 motion manual). My mom in law asked why are they selling her a car that is left with 5 mileage for a car to be taken to service and the salesperson insisted that she must drive the car for 15 mileage then she can take it to service this car was on 40 mileage the service plan book states that the next service is due in November. Today on the 02/01/2020 it's hardly 2 months she she bought the car she decided to take the car to a different place for service at Hyundai Sandton to get the 2nd opinion as the car was overheating from the day she bought it and the radio stopped working due to the car overheating. Aircon was and is still blowing hot air. When she went back to Kia Fourways she was told that they cannot assist her because the parts are not available and they cannot give her a new car because the manager is not there. So I want to know isn't it dangerous to drive a car that is overheating she bought this car for business (Taxify) now everything must stop because of your company wanting to push stock instead of considering their customers safety? At Hyundai Sandton they discovered that the problem was with the aircon (Re gassed aircon and they found a leak from the condenser. I want a new car and as for my business stopping due to your company giving me a car that is not on a good condition I want all the money that I make everyday I can even show you my statements to prove how much I make per day from taxify. Kia motors Fourways employees including their management are not customer centric. This ****** Gladness Bosman did not even bother to check service plan book, my mom in law contacted her to inform her that her car is overheating she hanged up on her while she was speaking what kind of service is this? Time of call 20:42 on cell number *** on the 01/01/2020. Gladness sold her a rental car and a salesman Mohammed confirmed that it was a rental car how I wished he was my mother in law salesman he has so much respect and he knows and understands customer centricity. I hate dishonesty if Gladness had told me that this car was used for rental she would've have bought that car never My contact *** I want urgent assistance as I need the money for taxify I cannot wait for Monday never.