They continue to call and leave no message.

I've been getting persistent calls from this number for two months now. Whenever I have answered it is a machine with two options, neither of which communicates to a person. It simply hangs up afterwards. This is driving me insane as the calls happen 3 to 4 times a week and usually around 7:50 - 8 am. If I don't answer there is a voicemail with the machine repeating the options. I don't even live in the United States!!! How can I get them to stop calling me???

Oh yeah, and it doesn't say who it's from! Just that I have a collect call. To get it option 1 and to place on hold option 2, something like that. Whichever I press the machine says 'goodbye' and hangs up. I'm tired of this.