In another swipe at its larger competitors, T-Mobile is now letting customers “stash” data they don’t use so that it can be tapped when needed for up to a year.

The new service, which T-Mobile calls "Data Stash," automatically banks unused data month to month. T-Mobile says there is no extra charge for the service and its available to new and existing customers, whether it's an individual, family or business account.

The customer must be enrolled in the company’s Simple Choice plan, and T-Mobile says it will start Data Stash accounts with 10GB of free data.

T-Mobile, the fourth largest wireless carrier behind Verizon, AT&T and Sprint, has been ramping up competition with its larger rivals with a series of “Uncarrier” announcements that have left the others scrambling for more competitive plans.

Over the year T-Mobile has introduced low-cost unlimited talk, text and data plans, no annual service contracts and the elimination of international roaming rates. Its strategy appears to be working.

The company, along with Verizon, gained market share among prepaid and postpaid subscribers in the third quarter, Cowen and Co. said in its quarterly wireless user survey report. T-Mobile had a market share of 4 percent, up from 3.4 percent in the second quarter, The market share was larger when postpaid subscribers were broken out.