AND THEY SAY THEY ARE THE EXSPERTS!!!

In March my car broke down what at work in Sandton, the engine would turn but not ignite, I call AA and they do their thing and advise me to take car to Renault, which I did. So I decided to take my car the dealership that does my services instead of the closest to me at the time. they however cannot find anything wrong and car starts for them even when the leave if over night. they then advise me to do a service and I thinking they know best said yes. so at the end of the day R6500.00 later with the repair of something else I am out of pocket. but guess what no go three days later car does the same thing, we manage to push start the car and I take it back to Renault and as this is a Friday afternoon I leave it there for the week end. Car starts on the Monday, they say their computer is not picking anything wrong up, BUT 4 days later same thing happens, this time after calling them they say the computer does not find any faults so practically tough lady. I then by chance find a small auto electrician whom finds to problem to be the crank shaft sensor which cost me another R16500. I want to know how Renault's 'TECHNICIANS\ could not figure this simple problem out "