I answer the phone and they hang up, very annoying.

Robo Call, when he finally came on line. He ask for owner. I ask wall call center he was calling from. He hung up.

Automatic Dialer. You can tell when there's no one on the line at first and then you here a 'boop' noise and someone who can barely hear you yells hello at you while there is static in the background. Very annoying.