T-Mobile (TMUS 1.12%) has officially passed Sprint (S) to become the United States' third-largest mobile carrier, but it's still well behind AT&T (T -1.06%) and Verizon (VZ -1.19%). 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.