iPhone SE
Apple iPhones such as the iPhone 6, 6S and iPhone SE support AT&T's Wi-Fi calling feature. Justin Sullivan/Getty Images

The problem with using your iPhone outside of the U.S. is that you’ll probably end up with a hefty cell phone bill if you’re placing calls or sending text messages while roaming. But with iOS 9.3, Apple smartphone owners on AT&T can now avoid those charges by making the call while connected to Wi-Fi.

The wireless carrier achieves this through a feature called Wi-Fi calling, which routes a cellular call through a broadband internet connection instead of a mobile signal. A call or text made to the United States or received from the United States while the feature is enabled on an iPhone won’t incur extra long distance and international roaming charges.

The feature itself isn’t entirely new. AT&T rolled out Wi-Fi calling in October 2015. But at the time it was aimed at customers who wanted to make calls in areas where a cellular signal isn’t readily available. AT&T also limited the service to areas where it could be used without additional roaming charges to the U.S., Puerto Rico and the U.S. Virgin Islands.

Since the update, AT&T has refreshed its Wi-Fi calling website to reflect the change. But there are a few caveats. While Wi-Fi calling is available abroad, its use may be restricted in some countries, and any calls made to an international number will still be charged at AT&T’s rate plans.

AT&T isn't the only carrier to also offer Wi-Fi calling. Other carriers such as T-Mobile and Verizon have also rolled out similar features over the past couple of years. The feature is available on the iPhone 6, 6S, 6 Plus, 6S Plus with iOS 9.3 and will also be supported in Apple’s latest 4-inch smartphone, the iPhone SE.