So I’m going to break my own rules and post a story about a non homebrew/jailbreak app, but I have to. iCall is what a lot of people have been waiting for. Many of us expected Skype to offer an application on the first day of the AppStore, but we are all still waiting! Oh well, the clever kids over at iCall are in beta testing for their app. Its not available to all of us yet, I will try and get my hands on a beta version but dont hold your breath. Here are a couple of things mentioned in their FAQ
Q: Is iCall really free?
A: Yes! There is no cost or hidden charge to use iCall to make or receive phone calls.
Q: Which phone calls are free?
A: All phone calls that you make to the USA and Canada are completely free, all calls that you receive are completely free regardless of where the caller is located. As well, all calls between iCall users are free.
So there you have it, pop over to the site here