Image: CNET

T-Mobile launched its eighth round of jabs as its cellular rivals -- this time focusing on so-called "data stashing."

The fourth largest U.S. cellular giant's chief executive John Legere said customers can keep data they don't use and store it for following months.

"Think of it as data rollover," Legere said, talking to Yahoo Tech's David Pogue.

"Now you don't lose what you don't use," he added.

The company's boss, whose time in the chair has been spent almost entirely on taking on its larger rivals, said this will help reduce the number of data penalties customers swallow each month for going over their allowances.

Legere said the "data stash" came from the people who spoke to him on Twitter, where he spends "most of his day," he told Pogue.

"Data stashing" is open to existing customers, but new customers will also be given 10GB of data for free to "store in the bank," and use as a reserve.

Unused data -- rounded up to the nearest megabyte -- will be banked into a user's data stash each month, with no upper limits on how much data can be stored.

Legere said this also applies to the company's business customers.

"I think this is really going to shake up the industry," Legere said.

The company has spent the past two years trying to working on just that, by aiming shots squarely at its larger rivals Verizon and AT&T.

T-Mobile's last Uncarrier event was held a day after the iPhone 6 launch in September to announce it was expanding its Wi-Fi Calling offering to areas of the country where users may not traditionally get service. In offering a Wi-Fi router dedicated to non-cellular voice calls, Legere said this was akin to "adding millions of towers to our network in a single day."

T-Mobile also struck an agreement with in-flight Wi-Fi provider Gogo, allowing T-Mobile customers to send and receive texts and pictures, and receive visual voicemail, on any global Gogo-equipped flight within the U.S.