Car Accelerates On Its Own problems of the 2002 Volvo V70

Over the past three years or so, I have had four or five incidences involving sudden acceleration of my 2002 Volvo station wagon v-70. All have occurred in city driving not on the open highway. Once when parking, I almost rammed another parked vehicle because, after applying the brake, my Volvo suddenly lurched ahead. I swerved, pressed harder on the brake and put the car in neutral. I then stopped. On other occasions, mostly when coming to a stop at a traffic light, the car slows down and then surges ahead, after applying the brake. Once again, to stop the car I had to slam down hard on the brake and put the car into neutral. On other occasions, after stopping at a traffic light or stop sign, the engine revs up to the point that I have to put it into neutral to stop the revving. I have brought the car into the martens Volvo dealer and explained the problem each time I brought it in for servicing. They have adjusted the "throttle mechanism" each time but the problem still persists.