Called several times today, I pick up the phone but do not say anything, so they do say hello but than hang up.

This number has been calling constantly saying they are from AT&T, but on the caller ID, they are identified as "unknown". We keep telling them to take our number off their list, but they constantly call. For example, today they called us 4 times. We ignored each call, because it's practically impossible to talk to them and get anything through their head. Once I picked up and the lady was frustrated and replied, "UGH" when I told her my boss was out of office. I don't believe they are with AT&t at all.

AWESOME!

Caller hung up the first time.  The next time we answered, the caller said that the Verizon contract was up and they were calling about current rates.  Beware.