Who called from 7204777267

Received a call from 720-477-7267 on 8-21-15 at 10:51am from "Unknown Name".
I don't answer calls from "Unknown Names".  720 is a Colorado Prefix

Called back and someone answered and said hello.  I explained i had received a call from this # and had actually received several calls.  I asked who they were and got no response and they hung up.

Calls and hangs up

called, I answered, no response, I hung up.