Pump not turning off even when system pressurised

How do you know the pump is not turning off?

Pull the grey cover off the switch and check to see if the points are open or closed. If they are closed, and they would have to be for the pump to be on, then either the switch needs adjusting, needs replacing, or the little pipe leading the switch is clogged and needs cleaning/replacing.

jlisenbe gave you top notch advice. Check that the contacts aren't welded shut and check the small tube from the pump to the control box isn't clogged.
Either one would give you the problem that you have. Good luck, Tom