Calls repeatedly for a few hours, every month or so. Never answers, only beeps.

I have the sam eproblem, it happens every couple of months.  
Same as Al above, you can't call back and the calls will continue for hours.

This number has been driving us crazy too- A couple times a month it starts, and it will keep calling back every 5-10 minutes.  It only beeps, and calling back gets the "number no longer in service" message"  A real PITA!

this number shows up on caller I.D.
All you hear are beeps like waiting for a fax to answer