Faulty car problems

I bought a car at Middleburg Motocity last month on the 17th and 5 days down the line the car was already giving me problems, I contacted the dealership people and they said I should bring back the car for them to fix it, I did that but it still gave me the same problems and now I am trying to get them to take it back, I have contacted Nedbank MFC and sent them a letter of complaint as they are financing the car but they haven't helped me with anything. The car has been at the dealerships premises since the 12th of this month and they are always driving around with that car. Please help me get the dealership to take back their faulty car.