From http://www.businessinsider.com/att-unlimited-data-plan-hbo-free-2017-4
OK, I've lost my FAN discount when I moved to the Unlimited plan but now this helps with the increased cost.
AT&T says that “Unlimited Plus” subscribers who pay for HBO already through one of the company’s video services, like DirecTV or the DirecTV Now live streaming service, will now get HBO for free. Those who don’t use one of AT&T’s video services can redeem the channels through DirecTV Now or the HBO Go app. And those who subscribed to an AT&T video service, but not HBO, will now get access to the channel automatically.
OK, I've lost my FAN discount when I moved to the Unlimited plan but now this helps with the increased cost.