2000 Chysler Grand Voyager vibration when I use the brakes

I purchased my car 17 months ago. The service replaced the rear brake pads and drums 4 months ago. After replacement of the rear brakes, there was a vibration on the steering wheel, brake pedal when I use the brakes. Passengers are also feel the vibration, and there was a noise. My service said that front is old, rear is new, therefore there is a vibration so my front brakes pads and rotors are replaced. After a week all the problems came back. My service could not find the problem.
I had wheels balanced and rebalance. That did not help. I went to another service. They said the previous service used the wrong rotors. They replace new brake pads and rotors. My problem still exists. I don't know how can I fix problem. Do you have any idea where the problem is?
Thank you.