T-Mobile USA has begun offering the iPhone 5 on pre-order ahead of its launch of the Apple smartphone on April 12. The development — reported by TechCrunch — is significant as it is the first time that the operator has sold the flagship Apple device, and it introduces a new pricing structure that removes annual contracts.

The device will run on its 4G network and includes a new plan that separates the cost of the handset and price of a customer’s calling plan. The iPhone 5 is available upfront from $579 (for a 16GB model) but, under the new pricing announced last month, a user pays T-Mobile USA $20 per month for two-years for the device, on top of their separate calling plan. This arrangement gives them the freedom to opt for the default month-to-month T-Mobile calling plan, or switch to another provider should they prefer.

On the base plan  — which includes unlimited text, talk and Web — the total cost of the iPhone and contract over the course of two years (approximately $1,780) is relatively cheap in comparison to competing carriers; but it pales in comparison to those in Europe.

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T-Mobile criticizing AT&T on stage. Image via CNET

The news follows yesterday’s announcement of T-Mobile USA’s first customer growth in four years. Its total customer base rose by 579,000 during the first quarter of 2013 to reach 34 million users.

Prepaid services were the primary source of that rise — as the operator added 202,000 new pay-as-you-go customers — while postpaid customer net loss was 199,000, that figure represented a 61 percent improvement on the final quarter of 2012, when the operator lost some 515,000 contract users.

The iPhone is a real sweet-spot for the company and, speaking earlier this year, CEO and President John Legeregere revealed that T-Mobile USA was serving 1.9 million iPhone users, and adding 100,000 new iPhone customers per month.

Last month saw T-Mobile USA announce that it would carry the iPhone 5 and, despite an Apple Store outage that some connected to today’s launch, the operator is not yet listed among the US vendors of the phone on Apple’s website.

Headline image via Yoshikazu Tsuno/Getty Images