The carrier had begun offering its Unlimited Plus subscribers free HBO earlier this year, but will now give the service to its midmarket Unlimited Choice plans as well.
Starting Friday, September 15, new and old AT&T Unlimited Choice plans will get unlimited HBO content added to their list of benefits, previously including standard definition video streaming and a maximum of 3MBps data speed for "normal" browsing.
The No. 2 US wireless carrier in April offered free HBO to some customers on unlimited mobile data plans.
AT&T's $85B takeover of Time Warner is still waiting on approval from Brazilian regulators and the U.S. Dept. of Justice.
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While AT&T is looking to bring in more wireless customers to their service through the HBO bundle, Randall Stephenson, AT&T's chairman and CEO, said on Tuesday that the company will also continue to pursue sales of HBO as a cable add-on. The subscription - which costs $60 a month, with additional discounts for people who have multiple phone lines on the same account - includes unlimited data, talk and texting capabilities.
Under the current offer, AT&T Unlimited Plus and Unlimited Choice customers will get a $25 monthly video credit toward HBO on applicable AT&T video services.
Stephenson also reiterated that Time Warner will operate as a separate subsidiary, which will be headed by John Stankey (who now heads AT&T's entertainment group).