Call or be called to/from anywhere in the world. Using WiFi.
If you have an iPhone OR an Android Smart phone you should
check out this web Page
http://www.viber.com/en/
Both you and the other party should be registered on viber
and you can chat by phone or video for as long as you want absolutely free.
It works by using WiFi over the Internet - VOIP.
Edit: You should each be in the other's Contact List on the Mobile Phone, that way you automatically show up in each other's viber when opened.