Facebook is quietly rolling out a new feature that could fundamentally change the way you make calls. A free call button has appeared in Facebook’s Messenger app for iPhone, allowing users to place a call over Wi-Fi or their cellular data network to their friends, the Verge reports. Facebook had been testing the feature in Canada since earlier this month, and it was being expanded to US users beginning yesterday. In the Verge’s tests, the call quality sounds good. There’s no video feature yet, nor any word on when the service will be available on Android or through the main Facebook site, but odds are those things are in the works. Of course, VoIP calling isn’t exactly new—Google and Skype have long offered apps of their own—but Facebook is different, Chris Gayomali at the Week points out, because “the slice of smartphone owners who are also on the billion-person-plus social network is considerable and growing larger by the day.”