How to Make a Free iPhone Call without a SIM in Google Talk

1. Tap the 'Settings' button, then tap 'Wi-Fi.' Scroll through the list of available networks and tap the name of one without a 'Lock' icon next to it -- or, if only locked networks appear, tap the name of the one you have the password for, input the password, and tap 'Join.'
2. Press the 'Home' button, and tap the 'AppStore' icon. Tap 'Search' in the bottom-right corner, input 'Google Voice' into the field, and tap 'Search.' Tap 'Install' to install the application onto the iPhone.
3. Tap 'Google Voice,' then tap 'Dial.' Enter the number you wish to call, keeping in mind that only U.S. phone numbers are free using Google Voice.