Bad service

My car was almost 92 000km and it was still under warranty when i has a faulty throttle body. I took it to ford garage to be fix and it was clean, i was told that the cause of the issue was because the car is used on gravel road and i was assured that the problem won't occur. Two months down the line similar problem occurs and i took my car back there to Ford Galactic Auto. I spoke to the Service Manager and he assured me that they will sort it out and the problem will never occur, should the problem arise the will change that faulty part (throttle body) i then ask when are they changing the part are they waiting for the car to be out of warranty so that i can pay? Last October i took the car back to the dealer and i was to that problem part was the battery and my record was deleted accidentally on the system.