Go to Autozone and buy a can of CRC Lectra-Motiv electrical parts cleaner. Put the spray extension on and spray around the switch. Push the switch gently to one side and the other with a small flathead screwdriver so you can get some of the cleaner into the switch itself.
Let it sit for five minutes and then try to release it.
If that fails you need a new switch but I bet it works. This also works for the cruise control, mute button and reverse switches that also get gummed up with road grime.
If it doesn't work, quit being cheap and replace it!