sana, international calls are not free, but the rates are apparently pretty good. Here is a link to the rates:
https://www.google.com/voice/rates The rates are US rates, because of the language setting in #1 below.

Comparison of Google rates with other companies': http://www.google.com/chat/voice/compare.html

1. It's available in the US - which means you go into your Settings on Gmail and change the language to English US.

2. Overview of Google Voice short video: http://www.google.com/googlevoice/about.html

3. Go here to install the Voice and video chat: http://www.google.com/chat/voice/

4. More detailed info: http://googlevoiceblog.blogspot.com/

Click on the green telephone handset at the top of your Contacts list, and then use your mouse to click the numbers on the pop-up keypad. While you are dialing, you will see a rate in the upper RH corner of the keypad - but it will change to "Free" once the number is typed in and "Call" is clicked.

Hope this makes sense....