Sprint is activating free unlimited Wi-Fi Calling on Samsung Galaxy Mega and Samsung Galaxy S4 Mini devices with an aim to further expand their portfolio with new devices later this year.

Sprint, the third largest wireless carrier in the U.S., is clearly aiming at dominance in the highly competitive market crowded by the likes of Verizon, AT&T and the rapidly growing T-Mobile. In an attempt to lure subscribers to its network, Sprint announced Wi-Fi Calling as a seamless solution for poor network coverage issues enabling free unlimited calls from Samsung Galaxy Mega and Galaxy S4 Mini. The over-the-air update to these devices will be rolled out in the next few weeks with more devices to get the feature later this year.

Sprint's Wi-Fi Calling battles the mobile network coverage issues at home and office due to various factors affecting the network. The updated devices will feature Wi-Fi Calling option that will also save cellular minutes on the network, similar to mobile data when it is connected to Wi-Fi. Sprint offers unlimited free minutes as a part of most of its modem plans.

Along with a reliable network, Sprint Wi-Fi calling will also improve the voice quality of the calls, according to the company's press release  , issued Friday. "Wi-Fi Calling is a FREE service that lets subscribers use their voice and messaging services over existing home, office and public Wi-Fi networks," the carrier said. "With Wi-Fi Calling, Sprint customers will experience improved voice, data and messaging services in locations that previously had limited or no mobile network coverage."

After updating the device, Galaxy S4 Mini and Galaxy Mega owners will be the first to have access to the service. The update will take mere two to three minutes for installation, during which the device will not be accessible to the network for calling or messaging. After installing the update, users can activate the feature by selecting Wi-Fi Calling icon under Apps folder and start making calls.

T-Mobile, the biggest competitor for the carrier, was the first to launch this Wi-Fi calling and messaging service. Sprint uses a similar method of using existing home, office and public Wi-Fi networks to improve network coverage. AT&T, the second biggest carrier, has built an extensive network of Wi-Fi hot zones in most popular areas to help users get a reliable network. This technology is widely adapted and anticipated to expand for better cellular use.