It is called DirectTVNow. It will work on a whole bunch of 'streaming TV devices'; https://www.directvnow.com/rokunow#how-to-watchAT&T has a new form of Direct TV; can't recall if it's called Direct TV Now or What but it is a Roku service and must be used with a firestik according to the woman at AT&T who wants to set me up with it. It costs about $35.00 a month.
But... I suggest you just get a Roku or Firestick w/o DirectTVNow first. There are thousands of channels available on Roku (you have to add them), and many are free. Having Amazon prime gets you more for 'free'. Internet search "roku free private channels" will show you hundreds more (though many don't have current stuff). If that isn't enough for you to watch, get a NetFlix Basic for $8/mo. I've had a Roku for years and haven't run out of things to watch (when I do watch TV other than local channels).