2003 Chrysler Sebring Power Door Lock

The power door lock switch does not lock the doors. Have to manually press the door lock plunger/s. But when driving above 20 mph, it automatically locks all four doors (which is the normal thing). Likewise, when opening the drivers door (car at halt), it also unlocks all doors (which is also normal). Is the door lock switch at fault? If yes, how do I replace it?