Poor Service experience

My Audi A4 2.0 T ambition was booked at Audi Sandton a month ago for an oil leak. It was released 2 days later and after two days of driving the oil lamp went on again. It was taken in the following week and they took it for 1 day. The drive was better however it was after 800 km it started showing engine light and EPC the car has been gradually loosing power since then. They took it on again a week and a half ago and promised me everything was fine. The situation just got worse I'm not sure whether the service department knows what they doing. Yesterday the 26.12.2017 at 13:00 pm I parked at BP Edenvale North and filled up the tank and after that it wouldnt start. I had to ask my insurance for road side assistance. This is way too much I have lost faith in the brand and need intervention from a senior personal.