Here’s a nice surprise for current and prospective AT&T customers that will brighten up your weekend: AT&T is offering a special limited-time promotion that will double the size of your data plan. Beginning Sunday, September 28th, and running through October 31st, Mobile Share Value plans with between 15GB and 50GB of data per month will see those data buckets double in size. This means that subscribers with accounts with two or more lines will have twice as much data each month without subscribers having to pay an additional penny.

This is how the promotional data plans break down:

This is a promo that families and big data users will undoubtedly appreciate, and it is available to new and existing AT&T subscribers alike. Of course, if you’re a current customer with a plan listed above and you want to see your data doubled, you’ll need to contact AT&T customer service or go to an AT&T store to switch to the new promotional plan.

Of note, while these new plans are part of a limited-time promotion, the increased data plan sizes do not expire; if you switch to a promotional plan before November, the size of your data bucket will remain doubled until you cancel your service or switch to a new plan.

Each plan still comes with unlimited talk and text, and more information can be found on AT&T’s blog.

Updated to clarify that the promotion applies only to accounts that have two or more lines.