The latest update for Google's new unified messaging platform, Hangouts doesn't support the outbound phone calls functionality.
Nikhyl Singhal, director of real-time communication products for Google said that they are working on adding outbound calls for the Chrome and Web extension. However, Hangouts at present supports incoming calls for users only with Google Voice numbers. For users, who want to make phone calls, can use Google Talk till the time the functionality in Hangouts is available again.
Singhal in his Google+ post said, "Hangouts is designed to be the future of Google Voice, and making/receiving phone calls is just the beginning. Future versions of Hangouts will integrate Google Voice more seamlessly".
The post was in response to the several complaints by users who were unable to make Google Voice calls from the Hangouts.Updated Google Hangouts Can't Make Phone Calls!,