Why does a washer over fill even when set on a level!

The water level switch is a pressure operated switch. It has a tube (hose) that connects the switch to the bottom of the washer tub. If it comes loose or gets a hole in it it will cause the washer to overfill. If there are no holes or loose connections in the tube. You should probably replace the switch. Make sure the tub is empty before connecting the hose and starting a wash cycle.

Is there only one hose that I need to check out and where would the switch be located at so that I could check that as well!
The water level switch is a pressure operated switch. It has a tube (hose) that connects the switch to the bottom of the washer tub. If it comes loose or gets a hole in it it will cause the washer to overfill. If there are no holes or loose connections in the tube. you should probably replace the switch. Make sure the tub is empty before connecting the hose and starting a wash cycle.

The switch is located in the control panel. It is connected to the knob you use to select load size. There should be only one hose connecting the pressure sensor on the switch to the side of the tub at the bottom. Usually it just a clear plastic or rubber hose.