Block voicemail without blocking the number completely


Mar 8, 2017
I am trying to figure out how to block a particular number from leaving a voicemail without blocking the number completely.

Basically I have a friend who calls me fairly often from jail and whenever I am unable to answer the phone right then it will automatically leave a useless voicemail containing part of the initial automated message.
He will frequently call multiple times in a row, since I can't call back if I just missed it, so I frequently have MULTIPLE stupid voicemails I have to go through and delete.

Is there a way to block the number he calls from from leaving a voicemail without blocking the call from coming through and me being able to pick it up if I'm available?
I've been trying to figure out the same thing. My voicemail says "please email or text me if you can" but my grandma leaves me long voicemails like 4 times a week and I end up missing important callers. We should patent this idea together :)