Who called from 2128844236

This number has called for the past two days in a row.  No message left.  Caller ID says "Unknown Name".  I'm not picking THAT up.

I answered because I wanted to challenge whoever it was, but as usual, no one responded to my "hello". That's how I know I'm on an auto-dialed call for telemarketers. I said "goodbye" and then blocked the number.

This is from Convergent, a collections company for Green Mountain Energy.

This is Convergent. http://www.convergentusa.com/
Mostly, they are bill collectors - especially for medical bills.