AT&T wireless customers who are on a Mobile Share Value plan will soon be able to roll over any unused mobile data into their next billing cycle, AT&T said Wednesday.

That's potentially a big boost for some subscribers. The change takes effect Jan. 25, and it covers everybody on a Mobile Share Value plan — new and existing customers. The data will only roll over for a month, though, meaning you can't stack up your unused data from February, March and April and hope to use it all in May.

AT&T seems intent on attracting more Americans to its Mobile Share Value plans. In November, some customers on those plans started getting extra data for no additional charge; people on 2 GB plans were automatically upgraded to 3 GB, and those on 4 GB were automatically upgraded to 6 GB.

The company's Mobile Share Value plan gives customers a communal pool of data that's shared across all devices on an account. For a single smartphone and 3 GB of data on a two-year contract, the plan costs $80 a month.

AT&T's latest announcement comes as the industry battle over pricing has intensified, with many customers becoming voracious data users. Last month, T-Mobile introduced its own data rollover feature, which goes a little further by allowing customers to keep unlimited amounts of unused data in their "data stash." That free data expires a year after it rolls over into the stash. And wireless companies have spent tens of billions of dollars in a recent auction of government airwaves that are crucial for delivering data and calls smoothly and reliably.