T-Mobile (NASDAQ:TMUS) has officially passed Sprint (NYSE:S) to become the United States' third-largest mobile carrier, but it's still well behind AT&T (NYSE:T) and Verizon (NYSE:VZ). T-Mobile has added over 1 million customers in each of the last nine quarters while Sprint is just barely treading water by adding tablet subscribers to make up for lost phone subscribers.

Here's how T-Mobile put Sprint in its rear view mirror -- and plans to continue grabbing customers from AT&T and Verizon.

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