Since I am partially disabled, the phone is right next to me.  When this number pops up on my TV screen, I pick up the receiver on the first ring, but I do not say a word.  I leave it off the hook until they hang up or the call disconnects.  I can hear them going "hello? hello? hello?" in some foreign accent (possibly mid-eastern), but I make no sound -- I even mute the TV sound.  Eventually they stop.  Then I report it to the FTC, which doesn't seem to do much good.  If the government or CIA or whomever is tracking our personal calls, why can't they track these calls and put a stop to this harassment?