• AT&T, Verizon, T-Mobile, and Sprint are offering free international Wi-Fi calling services through iOS 9.3 update.

AT&T, Verizon, T-Mobile, and Sprint are offering free international Wi-Fi calling services through iOS 9.3 update. (Photo : YouTube/Peyton)

AT&T and Verizon iPhone users are now getting international calling services via Wi-Fi connections at no extra cost. The service applies to the carriers' iPhone customers who upgrade to Apple's latest Operating System, iOS 9.3.

In a statement to some customers via PC Magazine, AT&T said, "With the latest software update for your phone you can use Wi-Fi Calling when traveling outside the U.S. This means you can call back to the U.S. or receive incoming calls, with no airtime charges."

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The carrier added that when customers call international numbers, their rates will remain the same as those in the smartphone plan or international package. AT&T started offering iOS-based Wi-Fi calling services in the United States, Virgin Islands, and Puerto Rico late in 2015.

Through the new OS, iOS 9.3, AT&T is expanding the service for international calling. On the other hand, iOS 9.3 is the official start of the Verizon's support for Apple's Wi-Fi calling service.

Verizon began offering Wi-Fi calling on some Android devices in December 2015. The carrier started with the Samsung Galaxy S6 and Galaxy S6 Edge, rolling the service out as a software update in stages, according to Verizon Wireless. It confirmed in February that it would as well support Apple's iOS Wi-Fi calling service in future.

Wi-Fi calling service allows users to use Wi-Fi hotspots to make voice calls in areas that are difficult to get a cellular signal, such as inside a building. As soon as the iOS service is created, users' phones will use Wi-Fi calling automatically in regions with limited or no cell signal alongside a Wi-Fi connection.

Users can create the iOS service through their settings on their iPhones under phone settings and Wi-Fi calling options. The service works in the background, allowing them to make and receive calls in the same way they would on the carrier's cellular network.

Meanwhile, both T-Mobile and Sprint have been offering international Wi-Fi calling services on Apple's iOS platform for over one year. Apple unveiled its latest OS this week when it announced the new iPhone SE and iPad Pro. iOS 9.3 offers Night Shift, Touch ID, Notes, News, and CarPlay.

Watch the sneak peek below for more information on Wi-Fi calling services.