Update: As of October 8, Wi-Fi calling for AT&T customers is active. Follow the steps as outlined below to activate the new feature.
With Wi-Fi calling enabled, iOS 9 users will be able to route phone calls through a local Wi-Fi network, a feature that's especially handy if you find yourself without a cellular connection.
I was able to activate and use the feature without having to add anything to my AT&T account.
Here's what you need to do to begin using AT&T Wi-Fi calling on iOS 9:
- Launch the settings app
- Scroll down and select Phone from the list of options. (You can also search the Settings app for Wi-Fi Calling if you so desire.)
- Select Wi-Fi calling from the top of the list.
- Slide the Wi-Fi calling switch to the On position.
The next few screens will require you to confirm you want to enable Wi-Fi calling, as well as opt-in to the service. The biggest warning is in regard to emergency services. You'll also be asked to verify the address where you plan on primary using Wi-Fi calling, again, for emergency purposes.
If the service isn't available for your device yet, you'll receive an error page explaining as much but not until you're done with the setup process, which is odd.
After activating Wi-Fi calling on my iPhone this morning, it took about an hour for the "Wi-Fi" indicator to show up next to the carrier name atop my device.
As for placing or receiving a call over Wi-Fi, you don't have to do anything different. Your iPhone will handle it for you; just pick up the phone and dial.