Like others, I will often let a call go if I don't recognize the number. Robots tend not to leave messages. Also, if yo do answer, robots wait for you to say he

Like others, I will often let a call go if I don't recognize the number. Robots tend not to leave messages. Also, if yo do answer, robots wait for you to say hello before starting the recording. If you wait a couple of seconds, a human on the other end will say 'hello?' but a robot won't.