The T-Mobile iPhone 5 release date was less than a month ago on April 12, but the "Un-Carrier" has already managed to sell 500,000 units.

The success of the T-Mobile iPhone 5 seemed assured from the get-go. T-Mobile offers the iPhone 5 for only $99 upfront — significantly less than any of its competitors. The rest of handset's cost is defrayed by a monthly $20 charge.

According to Tech Crunch, Sprint managed to sell 1.5 million iPhones in its most recent quarter, which includes all iPhones, not just the iPhone 5. T-Mobile, meanwhile, sold a third of that in about a third of the time, indicating that demand for the T-Mobile iPhone 5 is very strong.

In a press release announcing its Q1 2013 earnings, T-Mobile CEO John Legere said the carrier's new contract-less approach has been working out for the company, as has the addition of a T-Mobile iPhone 5:

"Our first quarter operating metrics and financial results are showing positive impact from the changes we began making in the fourth quarter. Branded customer net additions turned positive for the first time since the first quarter of 2009 and our postpaid business has demonstrated significant improvement," said John Legere, president and CEO of T-Mobile. "We ended the quarter with strong operational momentum, which is continuing into the second quarter, driven by the successful launch of our Un-carrier 'Simple Choice' service plan and the introduction of the iPhone into our device line-up. Things only get more exciting from here, having brought T-Mobile USA and MetroPCS together to create the wireless industry's value leader and premier challenger."

The company did not reveal how many customers purchased the T-Mobile iPhone 5 on new contracts and how many were upgrades for existing accounts.