Google Voice is great, but it isn’t an entirely free voice-over-internet service if you have to pay a phone bill to use it. With a few tweaks, though, you can make completely free internet phone calls with Google Voice.

What You’ll Need

* Google Voice account: Google Voice is a free service that, as of June 22nd (today if you’re reading this when it published), is available for everyone in the U.S. and Canada. All you need to use it is your Google account, so head to the Google Voice homepage and sign on in to get started (if you haven’t already).
* Sipgate account & phone number: Both are free—even the real phone number that folks can call you on all they want. Sipgate has many neat services to recommend it beyond its free Sipgate One service-with some cheap hardware, you could set up what amounts to a very cheap digital phone network, in your house or with a small telecommuting team. For now, though, we’re just going to hook up a Sipgate One phone account and number up to Google Voice.
* Audio tools for computer calls: You can make and take phone calls using your laptop’s microphone and speakers, but if you’re going to be talking regularly, you’ll probably want to upgrade to decent USB headset with microphone.
* Cellphone with text messaging: Just for a verification code that Sipgate sends. You won’t need the cellphone to actually use your free VoIP setup.

More information [lifehacker]