BMW does not care

My BMW went into Autobavaria prior to my service plan ending. The complaint was about my onboard computer randomly switching off. This was a major concern for me because when i bought my car brand new the same thing happened and Alberante replaced the unit. I have not had issues since then till I took it in a few months ago. When i left they assured me everything would be working. However the same thing happened, so I took the car back, again inconvenienced without a vehicle. Again they assured me it was sorted. When it happened again Andries said it was now a BMW SA problem and his manager was handling it. I called to speak to her, she was not available, I left a message, she never called me back. This is utterly disgusting! Why are they making no effort to call me back or rectify this issue. My computer keeps rebooting! This is my second hello peter complaint for the same company and same reason. BMW after care seriously lacks!