One of the big new anticipated features in the just-released iOS 9 is Wi-Fi calling for AT&T iPhone customers. Though Sprint and T-Mobile users have been able to use Wi-Fi calling on the iPhone for some time, AT&T and Verizon have yet to deploy it. Wi-Fi calling makes up for gaps or poor coverage in a carrier's phone service by offloading calls to a Wi-Fi network and routing them that way.

While Wi-Fi calling with AT&T iPhones was expected to be available broadly with the launch of iOS 9, the carrier now says that it is delaying the availability of it pending approval from the FCC. Those that had beta tested iOS 9 prior to launch have been able to use the feature and will continue to do so, according to the carrier.

"AT&T tested Wi-Fi Calling through the iOS 9 beta and we are prepared to support commercial launch of the service once approved by the FCC," said the carrier in a statement provided to Phone Scoop. The specific approval that AT&T is waiting for relates to features for hearing impaired, which have traditionally relied on TTY technology. Wi-Fi calling uses a different technology, called real-time text (RTT), to provide a similar service.

As it stands now, the FCC has not provided a time table for when Wi-Fi calling will be approved for use by AT&T phones. AT&T has also not indicated when it will deliver the feature to devices other than the iPhone, though we expect that won't happen until after the FCC approval comes.