I don't know who they are, but the call a LOT.  I don't answer calls I don't recognize.  If they really wanted to "talk" to me, they'll leave a message, but they never do. They just always hang up.

I turned off my answering machine. I don't want these a**holes to get the impression somebody is answering my number. If I don't recognize the number, I don't answer it. I don't try to return the call for fear they pick up on that somehow.

They just called again. I didn't answer and I have my answering machine is turned off.