Having just launched Graph Search, a service that enables users to quickly search through photos, friends, places and members interests,  Facebook has now introduced free calling for iPhone users.

The service, that begun testing earlier this month in Canada, is now available in the U.S. iPhone users will now see a new “i” icon on their screen when viewing a conversation with a Facebook friend in the Messenger App. To make a call to that person, users just tap on “free call” and the call is made over Wi-Fi as well as cellular data.

The recipient of the call, will receive a notification on their screen saying  ”Mark Zuckerberg is calling” for example.

According to Endgadget a Facebook spokesperson confirmed that,  ”you can only connect with a Facebook friend who also has [the latest] Messenger installed on their iPhone” and that “it’s only available on iOS.”

While not the only free calling service available, although limited to iPhone users, Facebook’s new service could ensure even more phone time spend by users on the social network. .