All android cell phone users can use their phone for free call to any other android phone from any edge of world. For use this facility your must need a android cell phone (2.2 froio or all latest version) ,internet connection and a software. The name of this software is viber .You can download this software from Google play store     (http://goo.gl/xumYx )  
without any cost. It is a 7MB software. After the installation in you mobile it will use 12MB space in your mobile. You must use your personal phone no as your viber id to the first step of this software and when you enter to the viber phone book, you will see your entire friend whose are using viber application. Now you can call or massege your friend at free. You can also send a request to your friend for use viber from your viber software.((((((enjoy))))))