call all day long, almost every hour and never say anything

Got 7 calls from this number today, no message.

Keep calling and calling but never leave a message. Finally added them to my screen list with Comcast.

They keep calling but they hang up

It is a survey about the cost of college and the affordability.  They start talking and doing the phone survey on my answering machine.  Dumb enough that they thought they were talking to a live person.  Representative Dan Kildee was the "guest speaker" on this conference call.  The call burnt up 10 minutes on my voice mail.  Jerks.