Car jerking

Took my car there for major service and now it is jerking. They said I should take it back so that they can inspect and advise. Like really, my car was not jerking when I took it there. Advise how because they have to fix whatever problems they caused. Number 2, they said my timing belt is worn out, I have replaced and my 'worn out' belt is as good as new...Extra costs for me. Like really now!!!