BMW cant do fault finding and i have to Pay

I took my BMW to BMW Clear water for the following error<br> All error lights came on<br> Wipers came on<br> Car does not select gears<br> and Rev counter, Speed o counter and Fuel counter needles jump up and down.<br> They informed me its the Alternator and the Battery at a cost of R17000. when i got the car back it had the same problem so i took the car back for 3 days they could not find a fault and charged me R850 when i got the car back the error were still happening. then i took the car to BMW Boksburg the said its because of faulty wiring and charged me R3000 when i got the car back the errors were still happening the car is still with BMW Boksburg they will now investigate further and then Quote me yet again as I'm standing on R20850 for the same fault they cannot find. also BMW Clearwater and BMW Boksburg does not have courtesy cars so i need to rent a car every time at a cost of R1200 every single time. now yesterday i gave back the rental then the errors came back so BMW told me now i have to go and get another rental at my own cost because they don't have courtesy cars and if they do people with motor plans get preference. According to BMW i have to keep paying till they find the problem