Who called from 2164548103

This number keeps calling me.  It rings once and then hangs up.  No messages have been left and it's starting to become frustratingly annoying.  Does anyone know who or what this is?

It's doing the same thing to me wont stop calling me

It's the Revenue group.  A debt collector for medical bills.

I got this call on 12-29-12 at 8:56 a.m.  This is Saturday morning and the office isn't even open.  It is Revenue Group and is a debt collector.  I don't know why I was called.  It was a robocall.

Rings once and hangs up.