When Counter top button switch pushed to turn on (insinkerator) garbage disposal won't stop spinning

You need to check to see if it is wired with a relay or if the switch controls the power to the disposal. If the switch controls a relay then the relay contacts could be welded together which keeps it running. If there is no relay then simply replace the switch. You should check it all with a meter, first, however. Never do any electrical work without using a meter to see what is happening in the circuit; to do so is foolhardy. Check the switch to see if the contacts are stuck (after turning off power and checking with the meter set to "volts.") and if so, you know you need a new switch; if not, you need a relay wherever it is.