VW Service

My car went in for service October 2019. Last week barely 6 months later I got stuck when it was checked what was the problem they said it is the campbelt which has now also affected the valves. I believe VW should have picked it up when my car was there in October for seervice but nothing was mentioned about an old campbelt that needed to be changed. I paid over R8000 and was told a major service was done on my car but now I am questioning what exactly was done on my car. I am not happy with VW Midrand service at all.