X5 leaking oil after standard service and not fixed after taking back to Menlyn Auto

I have been a BMW owner for many years. I have an X5 Diesel with 38000 kms on the clock and took it for a routine service at Menlyn Auto on 9 December before going on holiday. Apparently only a brake fluid change was needed. I however got the car back and within a day the oil warning went on. I immediately proceeded to top up the oil on the 10th of December. On the 11th the oil warning started again. I phoned Menlyn Auto on the 12th and took the car in on the 13th for a check-up. They assured me it was fixed and I went on holiday. A day after arriving the oil light went on again and I had to have the car towed in to the nearest service station. After fixing the car the closest service station said that the o-ring of the oil filter was pinched. The best of all is that Menlyn Auto said that they only changed the brake fluid. Shockingly bad service not in keeping with your brand.