These are all a telemarketer for charities (Plano Lions for one). Here is what they do. The robo system calls, then hangs up! If you answer then your number is flagged in their computer as a callback. Then they call, and call and call. They call at 9:01 in the morning, they call at 8:59pm. These computers are programmed to call at many different hours to see when you answer. Then they program them to call during those "answered" hours.
I hate these frigging things and I'm a programmer (I write computer programs that run payroll).
They get away with it because charities are exempt!