There is no way to "turn it off" but why dont you call into customer service and have them "remove" the voice mail feature from your actual line, this will get rid of it permanently and will solve your frustration
I am same way. I hate voicemail. It is a pain in the butt to call and listen to someone yammer on about a free cruise I have won. I tell my friends do not leave me voicemail. Send a text as I can see it and answer it quicker.