If you're up for it, you can also Jailbreak your iPhone and install a Cydia app named 3G Unrestrictor from Kim Streich. This allows the phone to get around any

If you're up for it, you can also Jailbreak your iPhone and install a Cydia app named 3G Unrestrictor from Kim Streich. This allows the phone to get around any network limitations imposed by Apple/AT&T such as making a Skype call over the cell network. I haven't installed it, but it appears to have a decent following.