It is AT&T..although they leave a message they do no leave you a number to call back. when you call back the 1-404-847-1080 number they are unable to patch you to the service rep you were speaking to earlier, leaving you to wait until the service rep returns your call if at all.
AT&T called me from this number to follow up on a technical support issue that I had. They started to leave a message and then I answered it when I knew who they were.