Rhoda

Hi all. ive recently purchased a used Grand Chrysler Voyager and put it in for a service and to get the timing belt replaced. got the car back, drove it for 1 day and it conked out. The garage has had it for weeks now and i have just been told that the problem is that 4 rockers are broken. i believe this would have been caused by a fault with the timing belt but the garage is denying this. can anyone help?