We Rent Cars SA not keeping they end of the bargain.

I am so disappointed in We Rent Cars SA, first when they gave me the car end of last year it was making a sound on the engine belt and I complained but they kept on tightening the belt about 3 times instead of replacing the belt. Also I got stuck late at night far away from home with a puncture and I could not change the Tyre because the spare wheel the car came with is a size 14 and the car uses size 13 tyres so that tell me that the car was not properly checked before it was given to me. The car came without another belt which is for the power steering because all along I was under the impression that the car does not have a power steering. Now that car is at Bosch Rustenburg for repairs under warranty and it has been there for the past 2 weeks & 2 days but it has not been touched because Boch says Grsa who are warranty guys are delaying the process because Bosch wants to strip the engine to find out why is the engine is starting to overheat but Grsa says they not going to pay for the stripping of the engine to find the fault and now I'm stuck, can anyone give me advise on how to terminate this contracts based on the reasons I stated. Car is a Chev Spark Lite 1.0 and I'm paying R5120 per month for 4 years and a half even though first I was told I will be paying that amount fot 4 years only, I mean I am paying so much for a small car but I am not getting my money's worth.