T-Mobile (NASDAQ:TMUS) had a pretty great 2017, adding 5.7 million total net customers last year. That total includes 3.6 million net additions in the important postpaid segment, of which 2.8 million were postpaid phone net adds (the rest being other connected devices like tablets).

During the fourth quarter alone, T-Mobile enjoyed 1.9 million total net adds, continuing its string of customer growth as the company poaches customers from its larger rivals. CEO John Legere pointed out that this was the 19th quarter in a row that T-Mobile has added over a million net customers, while 2017 was the fourth year that the company added over 5 million net customers.

John Legere holding his hand out while speaking on stage

T-Mobile CEO John Legere. Image source: T-Mobile.

Hitting the high end of guidance

T-Mobile exited 2017 with a total of 72.6 million customers. That's pretty impressive considering the fact that the Un-carrier had 55 million customers just three years ago. Perhaps more importantly, those have all been organic customer additions, in contrast to customers added through acquisitions like the 2012 purchase of MetroPCS. That deal added about 9 million customers to T-Mobile's roster. Instead, T-Mobile's additions in recent years have been largely defecting from rivals, as ongoing initiatives continue to resonate with consumers.

Specifically within postpaid customers, T-Mobile was quick to point out that this is the 16th quarter where it has led in branded postpaid phone net adds. The company's guidance had called for full-year branded postpaid net adds of 3.3 million to 3.6 million, so it was able to hit the high end of that forecast.

Churn also improved by about 10 basis points year over year and 5 basis points on a sequential basis, and came in at 1.18% for the fourth quarter.

That was fast

It's been just over a month since T-Mobile officially approved its $1.5 billion share repurchase program, and the carrier has wasted no time whatsoever in buying back its stock. In December, T-Mobile bought back 7 million shares at an average price of $63.34 for a total of $444 million -- nearly a third of the authorization in less than a month.

The number of shares is a drop in the bucket compared to T-Mobile's total 832 million shares outstanding (less than 1%), so shareholders shouldn't expect a whole lot in the way of earnings accretion quite yet, but it should be pretty clear that this is just the beginning of T-Mobile's capital return strategy. Buybacks also provide T-Mobile the luxury of flexibility as opposed to dividends, which income investors expect to pay out consistently over time and ideally with annual increases. Management has full discretion over the timing and amount of share repurchases.

The announcements go to show that T-Mobile decidedly did not need the Sprint merger that officially died last year. The telecom is crushing it going alone.

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