*30 does not block a call to my VOIPo number from my cell.
(I like that it tells you what you did.)
Calling the cell back from VOIPo said "Unavailable"

*31 did unblock the VOIPo CID feature and the interactive response said so.

Another thought on the HELP subject
** for the long list of * codes would be helpful
"**30" for example for a one code description because you think you know its "Permanently Block Caller ID".

"**code" is a great idea.
"**3" could give you all the "*3_" features ...
Just thinking user-friendly