You can't really deactivate it but you can functionally disable it. Remove your recorded voice greeting so it becomes an anonymous generic canned computer greeting. Turn on stuff like Extended Absence, Do not Reply, etc. Fill it up with (10) saved msgs so no more will be accepted, etc.
Some phone operating systems (or dialing apps) will let you change your voicemail number - so you can subscribe to one or more paid/private voicemail services - which you can edit or erase.
You can msg the PM Mods and request they remove the feature from your account. I'm guessing they can do it (just like they can add a block to 1-900 dialouts, etc).
