An update to Google Hangouts for iOS adds a voice calling feature that allows users to make free calls in the U.S. and Canada. Hangouts will use your Google Voice number for outgoing calls and incoming calls to that number can be answered from your Hangouts app; if you're an Android user and can't find this feature on your Hangouts app, well, that is because it doesn't exist yet...Source: http://www.phonearena.com/news/Make-free-voice-calls-to-the-U.S.-and-Canada-after-update-to-Hangouts-for-iOS_id48453
