The latest estimates from Kantar Worldpanel ComTech show that T-Mobile (TMUS -0.06%) is seeing success with its new "Un-Carrier" strategy. T-Mobile's market share of U.S. smartphone sales has jumped to 13.2%, the highest it has been in a year. There are several factors driving those gains, including transparent pricing.

The new pricing strategy was unveiled alongside T-Mobile becoming an official iPhone carrier. Having Apple's (AAPL -0.35%) presence in the device lineup has also contributed greatly to the momentum, tapping pent-up demand. Roughly 29% of T-Mobile's smartphone sales and upgrades last quarter were for the iPhone, and Kantar believes the most popular phone within T-Mobile is the iPhone 5.

Larger rivals AT&T (T 1.02%)Verizon (VZ 1.17%), and Sprint have looked to emulate T-Mobile's strategy in certain ways, including early upgrade programs. AT&T and Verizon, though, are much more entrenched in the subsidy model, which consumers still largely prefer in the U.S. The market may one day be willing to transition away from subsidies, but not quite yet.

T-Mobile has perhaps the most potential upside since it's been the underdog for so long. The carrier's competitive position has strengthened recently, and it has also acquired contiguous spectrum bands that can be deployed toward additional network rollouts and upgrades.

In this segment from today's episode of Tech Teardown, Erin Kennedy discusses T-Mobile's recent successes with Evan Niu, CFA.