call blocking for a single phone number

Anyone know the best way to do this?
Whatever I try seems to cover all numbers..
out going or incoming..

What I need to do is block a single number..an incoming number
right now I can block stealth numbers, but if they turn that off, the call comes through..

any ideas?

Help is greatly appreciated..

nobody knows how to do this?
Or is it so obvious, that I am missing the simple?