Here is something that has worked for me: When an unknown number calls you, answer the phone and scream as loudly as you can into the phone like a psycho-that will knock them off their rocker, love doin that and did that to this number here too and will be glad to pick up the phone again to scream like a lil girl into it.
This number calls quite frequently and only occasionally is there a message. Please stop calling!! I'm not going to "press 1 to claim the free boarding pass!"