I believe you need to first remove (unscrew) the knob, then unscrew the black bezel ring underneath. It should have 2 or 4 holes in it, and you will need cir-clip pliers, or a "modified" fork should work in a pinch. If it is tight, try pushing lightly on the switch from behind to relive tension. After the bezel is off, it should come right out from behind.
