Unhappy client

I bought a car at Nissan Kempton park in February, only to find out that I was sold a faulty car. I bought it for uber business so I can have an income to support my family, after finding out about the issue i reported it, the first time they told me they can't find anything wrong, I went again and eventually they found the problem and it was on the gearbox so it was booked in for repairs I did asked this matter to be acknowledged as an urgent matter because i'm using the car for business and it pays it self so it can't stay long, tell you what the car has been there since the the first week of july 2019, those people don't care about customers they got their money and now i'm the one struggling, last month I had to make a plan to pay for the car. All I keep on getting is stories and empty promises. How am I suppose to pay for the car if its not making money? as ive mentioned that it pays itself. This has become a stressful matter I'm really ****ed off and dissappointed.