T-Mobile USA customers, your day has arrived, or at least the day when you can buy an iPhone and stay with the same cell phone service provider. On Tuesday, it was reported that T-Mobile will support the iPhone 5 starting in April. 

Coupled with T-Mobile's offering plans without two-year contracts, this could change the game of preferred cell phone carriers in the United States. Until recently, T-Mobile was the only one of the big four carriers that didn't offer the wildly popular smart phone, which already was available with Verizon Wireless, AT&T and Sprint. 

Here is how the T-Mobile deal with the iPhone was described by Wired. The phone will sell for $99, without a contract, but users will pay an  $20 for 20 months in addition to their monthly wireless and data charges. Or, to avoid the monthly $20 fee, interested buyers with enough cash on hand can buy the iPhone for full price up front.

Is the new system worth it? Will the up front payment or $20 paid over the months save consumers money in the long term. At least one observer believes that is the case. Over at International Design Times, the numbers show that over time a T-Mobile customers would save several hundred dollars as opposed to a traditional setup, where consumers get the phone on deep discount but are locked into pricier two-year contracts. 

"When I assessed the cost of the unlocked iPhone 5 upfront against the cost of the iPhone 5 subsidized and on a two-year plan, no matter where I went, be it Verizon, AT&T or other iPhone 5 retailers, in the long run the price of the smart phone would end up costing me a whopping $920 minimum at the end of my two-year contract," the International Design Times reported. 

All this could be very good news for T-Mobile, which remains in fourth place among the four main wireless carriers in the United States. But with rumors of an iPhone 6 on the way, the company's challenge is to convince people at other cell phone companies to break free when their cumbersome contracts are up. If they can do that, T-Mobile could expect some big growth in the future.