Don't hang up on T-Mobile (TMUS) - Get Report just yet.

The telecom carrier continues to lead the wireless industry with strong postpaid phone additions and, on top of that, its shares soared 9.5% on its third quarter earnings beat Monday, as well as it hit a new 52-week high on Tuesday.

But valuation concerns have been raised. And investors want to know if T-Mobile's above-$50 share price can be sustained. The fear is that the company's ongoing pricing war with larger rivals, such as AT&T (T) - Get Report and Verizon Communications (VZ) - Get Report , will pressure T-Mobile's profits, especially when combined with the investments it continues to make to upgrade its network.

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However, that has been the argument against the company for the past five years. And T-Mobile CEO John Legere, who has grown the company's stock value some 200% during that span, has done nothing but prove the doubters wrong. What's more, both AT&T and Verizon have become distracted with large M&A deals, according to Legere. For AT&T, it's the Time Warner (TWX)  merger and for Verizon it's Yahoo! (YHOO) , both of which Legere believes will provide the opening his company needs to gain even more subscribers.

T-Mobile added a total of 851,000 net new subscribers in branded postpaid phones during the third quarter. Compare that to AT&T and Verizon, which lost 268,000, and 36,000 net subscribers in branded postpaid phones, respectively. It would seem that Legere has already figured out how to gain customers from T-Mobile's larger competitors. And the fact that it has done so, while beating Wall Street's earnings estimates in four consecutive quarters suggests he knows how to get those new customers in a profitable manner.

In other words, despite the company's tactics, such as undercutting both AT&T and Verizon on price, it has yet to show an adverse effect on T-Mobile's bottom line, or its share price. And with both AT&T and Verizon now in a position to focus on bringing synergies to the companies' M&A deals, T-Mobile stands to gain even more momentum by ramping up its aggressive, but successful, promotional campaigns.

To that end, despite T-Mobile's shares climbing some 30% year to date, outperforming the 5% rise in the S&P 500 (SPX) , the stock should reach $60 to $65 in the next 12 to 18 months, delivering premiums of 15% to 20% on the strength of its subscribers.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.