When I see a number that I don't recognize I pick up the phone and listen but I do not say anything. If it's a machine waiting for a voice to activate it then I get dead air and the machine disconnects after a few seconds. If it's a bonafide human then I get a "hello is anyone there?" In this case I got an immediate disconnect. I reverse dialed the number and got the "out of service" beeping. I got the call about 5 minutes ago.