SAN FRANCISCO (KCBS) – T-Mobile announced this week it will sell more than 100 smartphone models with a built-in feature that taps into Wi-Fi networks to make phone calls and send text messages when customers can’t connect to the carrier’s cellular network.

The program announced Wednesday appears to be T-Mobile’s latest attempt to lure wireless subscribers from rivals Verizon Wireless, AT&T and Sprint.

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T-Mobile is trying to exploit the hoopla surrounding the release of Apple’s iPhone 6 with its new twist on Wi-Fi connections. The iPhone 6’s latest options include the ability to begin a call on a Wi-Fi network and then automatically transfer the conversation to a cellular network without interruption when the device is on the move. T-Mobile is the only U.S. carrier offering this versatility on the iPhone 6, as well as several earlier iPhone models if they upgrade to Apple’s latest software, iOS 8, after it’s released next week.

While other phones sold by T-Mobile will be able to start calls on Wi-Fi, they won’t be able to switch over to cellular network in mid-conversation. That means any call begun through a Wi-Fi connection on a device other than the iPhone 6, or upgraded older iPhones, will have to be completed on the same Wi-Fi network. T-Mobile, which is based in Bellevue, Washington, hopes to extend the capability to switch calls from Wi-Fi to cellular networks within the next few months.

Making Internet calls and texting through Wi-Fi already has been possible through several messaging apps that must be installed on smartphones. The feature will be built into all the smartphones sold at T-Mobile’s roughly 3,000 U.S. stores.

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