Poor service by VW

My mother took her car to VW for service at 45000km and there was no problem reported, and the brakes were at front brakes 7mm and the back brakes 9mm. When the car was new the brakes were at 12mm. When the car was at 53000km, the brakes and discs are said to be finished. Which doesn't make sense. We complained in writing and were given a case worker. Unfortunately the case worker knew nothing about cars and didn't resolve our problem even when we asked that the matter be investigated by someone who knows and understands cars. We are very disappointed.