Who called from 7084304076

Calls constantly and does not leave a message.

Calls as if a friend checking to see if you are out and then proposes a questions and disconnects.  The number is always busy if you try to call the number back.

Get several calls a day, and it is a fax tone when answered.

This number called our house.  The caller ID read "Cook County", as in the county in the Chicagoland area.  The person did not leave a message when we didn't pick up.  When I tried to call it back, there was a busy signal.  Is this coming from a cook county agency?

Do you think it is the prison scam where if you answer, somehow they charge collect calls to your number?