Same here, they call between 5 and 10 times a day. Never leaving a message or saying a word. They've even called as late as 9pm on a Saturday. I've reported this number to the do not call folks about a month ago. Yet the calls continue.
They have called me several times a day with no message as well. I don't get long distance on my home phone so that may be why they 'hang up' when I answer. It is so very annoying to have them call EVERY SINGLE DAY! I called the number back from a cell phone and I believe it maaaay be ATT but their hours are from 8-5 I think. It is ridiculous because I get calls from them up until 9pm. I just registered my home number, as I have my cell, to the DO NOT CALL REGISTRY.