T-Mobile announced today that it will begin selling Apple's latest iPhone, the iPhone 5, come April 12.

The carrier - the last major U.S. network to get the iPhone - promises the device will come to customers in a "new affordable, unrestricted and hassle-free way" via its new "Un-carrier" data plans.

For $99.99 down plus $20 monthly payments for 24 months, qualifying T-Mobile customers can pick up the phone. The device will be compatible with T-Mobile's LTE network, which today is now available in seven major markets.

The iPhone 5 will come with no annual service contract plus unlimited talk, text and web.

T-Mobile's new look

CEO John Legere called the partnership T-Mobile has forged with Apple in working to get the iPhone "the start of a long relationship." The iPhone 5 helps "fill a huge voice in our device portfolio," he added.

Select markets will also welcome the iPhone 4 and iPhone 4S, with the iPhone 4S selling for $69.99 down at $20/month for 24 months and the Four going for $14.99 down at $15/month for 24 months. These devices won't run on T-Mo's LTE.

T-Mobile's iPhone 5 will include HD Voice nationwide, making it the only carrier to do so. Through its Simple Choice plan, customers can also turn the phone into a hotspot, nabbing an additional 500MB of 4G data for tethering to iPads, Macs and other devices.

There's also unlimited simultaneous surf and talk.

The iPhone 5 on T-Mobile will support HSPA+ on AWS bandwidths and 1900 GSM frequencies as well as the 4G its so highly proud of.

Lock talk

For a carrier known for its openness to unlocking, it may come as a bit of a surprise to know that the phones signed up for with T-Mobile - including the iPhone 5 - will stay locked to the carrier until the device is fully paid off.

Furthermore, if customers get a phone they're not entirely happy with, they can trade it in at fair market credit for the device.