HBO Go

Tried to use the HBO Go app on my TV and followed the instructions (go to HBOGO.com...type in the code...select provider), however I receive a message stating I am not authorized and to verify my authorization. When I called AT&T, the representative had never heard of HBO Go. An hour and a half later I had to hang up because I was on hold so long. Anyone have any idea how to get this to work? I pay like $26 a month for HBO.