AT&T kicked off a new Mobile Share promotion that doubles data for customers on 15GB plans, without implying any additional charge.

In other words, customers on 15GB plans will now be able to benefit from 30GB of data per month, at no additional charge. Customers on higher plans will also get double the amount of data. The promotion is already in place and will last until the end of next month.

"Beginning Sunday, Sept. 28, AT&T is offering new promotional Mobile Share Value plans that include double the amount of data offered on Mobile Share Value Plans with 15GB to 50GB of data. New and existing customers who proactively sign-up by October 31 get 30GB of data for the price of 15GB - perfect for families and small business customers. AT&T customers will benefit from this offer, which includes unlimited talk and text, as well as unlimited international messaging from the U.S. to select countries," the carrier has announced.

Moreover, interested customers who sign up by Oct. 31 will be able to keep their new promotional shared data amount for an unlimited period of time, as there's no expiration date. Those who want to change their shared data amount once the promotional period ends, meanwhile, will need to choose from the current Mobile Value Share offers.

"We're now making our simple and flexible plans a greater value by doubling the data for the same price," touted AT&T Mobility Chief Marketing Officer David Christopher. "Families and small businesses can share a huge bucket of data on the nation's most reliable 4G LTE network, which now covers more than 300M people. With these new double data plans, and smartphones for $0 down with AT&T Next, there's never been a more affordable time to be with AT&T."

In conclusion, this limited time promotion will end on Oct. 31, after which the plans will revert back to their previous amount, but those who sign up in due time will be able to keep their doubled plans for life. It's also worth pointing out, however, that those on older AT&T plans such as Family Talk or unlimited data, will have to take one thing into account: these new plans will eliminate their subsidy, which means that they will force users to go for off-contract or AT&T Next phone options.