I get the NAD calls too, but we NEVER pick the phone up unless we Know who the caller is and they speak first . SO I SAY TO NAD OR WHO EVER YOU ARE KEEP CALLING MAYBE YOUR FINGER WILL FALL OFF....HOPE SO
Usually I never pick up unless I recognize who's calling. On those rare occasions when out of curiosity I do pick up (usually after the umpteenth daily call from the same unknown caller), the line is open, but no one says "Hello", even when I do so. So I hang up before the robo-dialer computer recognizes a human voice and routes me one of the people in that particular boiler-room.
Even though I'm on the "no-call" list, I still get unsolicited calls from several numbers. The "no-call" list doesn't seem to matter to these people.