If you posess Electronic Warfare skill, you can switch it on/off anytime you want by yourself. Otherwise restart would be enought.
Its just that when used for Jamming on fly, commlink cannot be used for anything else. So Ill bve unable to connect to turn it off.
+
it is
EW(4)+Signal(4) (8d6.hits(5)=2)against oponents roll (EW+Signal+ECCM if present)
So it is not sure it would work (well, EW cannot be defaulted, so no roll possible if there is no EW autosoft...)
EDIT: Modified IC, Sam had been instructed for case something goes south.