I receive call after call daily from this number. I'm so sick of it, who has time to keep answering the phone to hear something your not interested in hearing?? What can be done about this?

They keep calling and hanging up on me, we are a business, do not need to be answering the phone for phony calls.

We are listed on the DO NOT CALL list. How are they able to call our office? ...and I'm pretty sure you DO NOT handle out AT&T accounts.

These people call every day. I usually do not answer but today I was feeling it so I answered. He asked for whoever handles my AT&T account. I replied "Nobody. Don't call me again" He replied "Hey, hey hey don't you dare hang up on me!" I said I am not interested in anything you have to say to which he replied " You will be interested when we pull your AT&T line down" That was the last thing I heard as I was hanging up.
I have used call block on this number yet it still gets through some how.

Same here.  I don't get any response when I answer calls from this number.  It is annoying to drop what I'm doing to grab the phone and get dead air in my ear.  Sometimes it clicks a couple  times then I get dial tone.  My next step is going to the FCC website and filing a formal complaint.  If all of us would do that, it might make a difference.