2013 has been kind to T-Mobile's ever-expanding customer base following a trio of bold "Uncarrier" initiatives the nation's fourth-place carrier rolled out this year. However, there's apparently still more to come.

T-Mobile Chief Executive Officer John Legere served up a late-night Twitter tease December 17, an early virtual Christmas gift that gives customers even more to look forward to in the New Year.

"#ItsAboutCustomers -Time to eliminate another customer pain point? Time for #Uncarrier4? Yes it's time! Stay tuned...Happy New Year #Randall," the tweet posted at 11:54 p.m. tweet reads.

The hashtag #Uncarrier4 undoubtedly refers to the fourth phase of the carrier's plans to shake up the industry, although 140 characters aren't quite enough to offer much insight into what Legere and friends have in store for 2014.

Fourth time's a charm

T-Mobile kicked off its "Uncarrier" marketing campaign back in March when the carrier banished subsidies and two-year service contracts.

As it turned out, that was only the beginning: Uncarrier phase two introduced Jump!, a $10 per month program that allows Simple Choice customers to finance their handsets and even trade them in for a new one twice each year.

The Uncarrier trifecta arrived in early October with phase three, which introduced unlimited international text and data plus flat-rate voice calls in more than 100 countries.

A mini-shake-up followed two weeks later when T-Mo announced 200MB of free data for all tablet users on the network.

It's hard to imagine what T-Mobile could have up its sleeves with phase four - or when the latest move might arrive - but Legere's witching hour tweet is clearly a jab at rival AT&T, whose own CEO Randall Stephenson is referenced with the hashtag #Randall.

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