From what I understand, if info is correct, most of these calls are being made by an automated dialer. It just goes through a list one number after another and if someone is available to talk, if you answer, you will be connected. If not, you get nothing and it just disconnects after a few seconds. Also, they can program in any number they want to show on your caller ID. I have received calls showing my own number on caller ID. They must have a fancy program that changes the outgoing caller ID display to show the called number with each call.