As we reported last week, the latest beta version of iOS 9 includes support for Wi-Fi Calling on AT&T for the first time. This feature, which is exclusive to the iPhone 6 and 6 Plus, allows users to place cellular calls over a Wi-Fi network in situations where they have a poor cell signal.

To turn on Wi-Fi Calling, go to the Phone panel in the Settings app and select the Wi-Fi Calling option. It should be at the top of the second section, just below “My Number.” On this page you’ll find a single toggle. Turn that on to begin the setup process. You’ll be given some basic privacy information and asked if you want to continue.

At this point, the beta used to simply return an error message, but with the changes on AT&T’s side today, you’ll now see a lengthy a agreement that you’ll need to accept before you can proceed. It gives warnings about potential issues with 911 calls and some boilerplate disclaimers.

Once you’ve agreed to the terms, you’ll be told whether the feature is available in your area. If it is, you should start seeing it work over the next few minutes. If not, you’ll need to wait until AT&T enables it for your market.

As the disclaimer and agreement page notes, this appears to be a trial run of the feature. AT&T and Apple wouldn’t comment, but we’ve confirmed with someone familiar with the matter that Wi-Fi Calling is currently only rolling out in a limited number of regions. Support in additional areas is expected very soon.