AllThingsD reported on Monday that the fourth-largest U.S. carrier, T-Mobile (News - Alert) USA, is launching a new campaign this week to lure iPhone users, especially AT&T iPhone subscribers. As per this report, the carrier is asking customers to bring their own unlocked AT&T (News - Alert) iPhone and pair it with one of T-Mobile’s plans.

In an interview given to AllThingsD reporter Ina Fried, marketing director Harry Thomas said, “By taking out the cost of subsidizing the iPhone (News - Alert), T-Mobile can offer significantly cheaper rate plans.”

As per this report, T-Mobile plans to put a working, unlocked iPhone in each of its stores, and launch an “unlocked and unlimited” marketing campaign to attract more unlocked iPhones.

The report indicates that the service provider has already upward of one million iPhones without heavily touting the option.

In this new campaign, wrote Fried, T-Mobile is offering an unlimited data plan for unlocked AT&T iPhones, which it reintroduced last week. With plans starting at $60 a month, the AllThingsD report shows that T-Mobile can save heavy data users more than $50 a month compared to AT&T.

Although T-Mobile said it will not sell used iPhones, the company’s marketing director told AllThingsD that there are plenty of them available on the secondary market. The number-four carrier also indicated that it will not do the physical unlocking of devices.

But AT&T will unlock iPhones for customers who have fulfilled their contract and are in good standing.

While the offer looks attractive, there is one major problem with T-Mobile’s pitch, according to Fried. “Its network isn’t yet all that iPhone-friendly given that its high-speed network has historically run in a band of spectrum not supported by the iPhone.”

Though T-Mobile is in the process of addressing this problem so that Apple (News - Alert) iPhones can run at full speed, for now all customers will be running at far slower 2G speeds, Fried wrote.

However, the report indicates that T-Mobile is in the process of upgrading its network cell tower by cell tower to support the frequencies used by iPhones.

Meanwhile, Apple is preparing to unwrap the next iPhone this week, expected to support LTE (News - Alert), the 4G high-speed network. The report shows that T-Mobile is not expected to launch LTE until sometime next year.

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