AT&T is once again going to offer an unlimited data plan, but only if you are also a DirecTV or U-Verse subscriber. Most U.S. carriers have moved away from offering unlimited data plans and towards data buckets for families, but AT&T is going backwards here and will begin offering the new plan, but it obviously comes with a catch. You won't be able to just sign up for AT&T or change your current plan to the new unlimited plan without subscribing to either DirecTV or U-Verse.

If you happen to be a U-Verse or DirecTV subscriber with AT&T as your mobile provider of choice, you'll be able to sign up for the new plan for $100 a month for a single line, and $40 more for each additional line you add. Should either of the providers be your television choice, but AT&T not your mobile carrier, AT&T is offering those who switch $500 in credits with an eligible trade-in. During this limited time promotion, the carrier will also be offering the fourth line for free each month, meaning you can have four lines with unlimited data for $180 a month, should you meet the requirements here.

Source: AT&T