Viber - Free Phone Calls & Text
@karasicpark says: "I love this app. I can talk to people on the other side of the world using my wifi, and use the interface of the iphone, with my iphone phone number, my address book, the iphone interface. Pretty seamless. You just have to remember to add a "+" sign when adding foreign country numbers. I think for making wifi calls it's easier to use than skype. And the reception is great."