Google Hangouts

Hangouts—the popular app from Google—gives you the ability to get in touch with other Google users via messaging, video calls, and phone calls. 

You can use Hangouts to:

Start a chat conversation or video call.
Make phone calls using Wi-Fi or data.
Send text messages 
Hangouts sync automatically across devices. If you start a Hangout on your computer, you can continue your chat on another device, like your phone.