Accelerator Stuck problems of the 2006 Chrysler 300C

I had taken the car for an oil change. When I got into the car and started to pull away from the shop the accelerator pedal stuck in the down position causing the car to surge forward. I was unable to stop the car using the brakes and struck the bumper of a parked car with the passenger side of my car. The car still would not stop so I turned off the ignition. The car stopped. I put the car in park and restarted the engine the rpm immediately went to more than 4000 rpm . I turned off the ignition and manually pulled up the accelerator pedal the engine idled normally after restarting. I drove the car to the dealer and left it with them. The accelerator continued to stick in the down position and required manually returning at each time I needed to slow down.