AT&T International Day Pass
An AT&T store sign in Broomfield, Colorado, April 20, 2011. REUTERS/Rick Wilking

In the heated competition between AT&T, Verizon, Sprint and T-Mobile for customers on the new unlimited data plans, AT&T just played a wildcard.

The wireless carrier announced a deal Wednesday that offers customers on the “Unlimited Plus” plan HBO subscriptions at no added cost, a $15/month value.

Read: Best Unlimited Data Plans: Verizon, AT&T, T-Mobile, Sprint All With New Offers

The offer will be available to new and old customers starting Thursday, April 6, said AT&T in a release. The unlimited plus plan costs $90/month for one line, $145/month for two lines and each line thereafter is an additional $20. The plan includes a 10 GB hotspot, unlimited talk and text, unlimited data for all your streaming needs and now HBO.

The deal also applies to customers who are on the unlimited plus plan and already pay for HBO through a video service, those customers will now have HBO at no cost and customers who have an AT&T video service but do not have HBO will now have it for free.

All of the wireless carriers have been in close competition for customers since T-Mobile announced it would offer customers unlimited data plans back in January. Other carriers then followed suit and a month later all the major carriers were offering similar plans at close prices.

AT&T’s new offer is the next step in staying competitive. No other carriers have announced a perk like the one AT&T is offering, yet.