Facebook’s free voice calling service has begun rolling out to users in the U.S. after a trial in Canada that began earlier this month.

As first reported by The Verge, voice calling will be made available to U.S. users with the latest version of Messenger for iOS starting today and will gradually be brought to more users.

Users can call their friends — who also need the latest version of Messenger for iOS and to be part of the initial test group — by tapping the “i” icon in the top right of the screen when messaging a friend and then tap “Free call.” The profile picture of the user being called will take over the screen and a ringing sound will play as the call attempts to connect. The recipient will get a push notification about the person who is calling. If they miss the call, they will see a notification and a record of the missed call will be included in the users’ conversation history. These calls are voice-only and are not cross-platform.

Facebook calls are free but contribute to people’s data usage unless they have a Wi-Fi connection. There are a number of existing voice calling services that are also free, but they require both parties to have downloaded the application. With Facebook’s ubiquity, this is less of a hurdle.

At the start of January, Facebook added asynchronous voice messages to Android and iOS Messenger. Users can send each other voice messages up to one minute long. This feature is similar to mobile walkie-talkie apps, which can be used for fun or utility, for example when a user doesn’t want to type a long message or doesn’t want to interrupt someone with a phone call.