As far as I know, NO. THERE IS NO WAY TO DEFAULT THE VOICE MAIL.
But you can do this. Reload a default back up.

Do you know how to do a back-up and a restore.

If so I have a default back-up file I could send you. Make sure you keep the a-1 file.
COPY THAT A-1 FILE. This file is very important.


But i have to say, you don't have to do much to deleted everthing.