SERVICE THEN PROBLEMS

My Jeep Compass went for a 30 000 service on Monday 20th of July ,nothing was wrong with the car ONLY A SERVICE WAS NEEDED .I received the car back washed and all good (that is what i thought ) Wednesday the 22th of July the cars head board was like a Christmas tree all nice and red. The manual indicated that the throttle was giving a problem. So the car went back ,only to hear that the throttle thing has broken.Tell me how do they get it right.JEEP South Africa told me that maybe the tech don't know what they are doing or they haven't had the right training. I have phoned about 3 different places and all tell me the engine was washed and the cables must have got wet .Now this is the second Jeep i have had in less then 1 year .First engine problems and now throttle problems