Bad service

I bought a used combi from Hyundai Roodepoort(Gert) with the installment if less than 5000pm in hope to start my own transport business, in the past five months that I've had the car it's has broken down countless times, I've only had it in my position for less than 3 weeks in total. Now I've lost the kids I used to transport due to their car being unreliable. Their manager Theo said they will settle the car and give me a reliable car with just an extra 300, but instead they put an extra 3000. After I told him there was no way I can afford it he tells me that it's none of his business and says they will give my old car. Tis garage takes advantage due to the fact that I am a woman and know nothing about cars. I don't want that ****py car anymore, am sick and tired of Hyundai Roodepoort