T-Mobile’s latest uncarrier move saw CEO John Legere take aim at the “scam” that sees Americans pay $1.5 billion in overage fees each year.

The company’s new feature called ‘Data Stash’ will allow users to roll over their unused monthly data into the next billing cycle.

There is no limit to how much data customers can collect in their Data Stash, which comes with the slogan ‘what you don’t use, you won’t lose’, but it will expire after 12 months.

Data Stash will be available from January 2015 and will be included at no extra charge for all new and existing T-Mobile customers – individual, family or business – on a postpaid ‘Simple Choice’ plan for those who buy additional 4G LTE data, 3GB or more for smartphones and 1 GB or more for tablets.

When users sign up for the service, they will also receive 10GB of 4G LTE data for free, which will expire at the end of 2015.

Speaking to technology writer David Pogue, CEO John Legere claimed the move was “the biggest thing we’ve ever done since uncarrier 1” (when the operator did away with contracts in March 2013).

Describing data that expires every month as a “pain point of staggering proportions,” Legere – who claims he detests the current structure of the industry and wants to change it – also said it is unfair to expect people to know how much data they will use.

To avoid penalties of breaching data limits, Legere said consumers often end up overcompensating and buying extra data. On average, the CEO claims a customer has 3GB of data left over every month, which means they are paying around $480 for data they are not using.

Legere says he wants all such ‘overages’ to be done away with, calling them a “total scam” and “exactly what uncarrier was made to handle”.

The charismatic boss said T-Mobile’s inspiration for Data Stash was seeing 40,000 customers on Twitter asking their carriers to allow for data roll-over.

“We are the only ones who cared enough to listen,” he said.

As for how long the operator will continue to pay off people’s early termination fees to give them incentive to switch to T-Mobile from rivals like AT&T and Sprint (part of an earlier uncarrier strategy unveiled at CES 2014), Legere said: “We will stop when there is no contract on earth left.”

LTE growth
As part of the uncarrier 8 announcements, T-Mobile also said its LTE footprint is growing and it now reaches 260 million Americans. It says it is on track to cover 280 million people with LTE by mid-2015 and will reach 300 million Americans by the end of 2015.

Following the upgrade of its network to ultra-fast wideband LTE in New York, the operator says it reaches 121 metropolitan areas across the country with wideband LTE services. It claims T-Mobile customers in the NYC metro area have reported download speeds “in excess of an unprecedented 100Mb/s.”

It has also deployed its newly acquired 700MHz spectrum in Cleveland, Colorado Springs, Minneapolis and Washington, D.C.

Meanwhile T-Mobile is seeing an average of 19.2 million VoLTE calls and 6.6 million Wi-Fi Calling calls by its customers every day. Its smartphone customers use an average of 3.5Gb of data per month.