Apple have recently removed restrictions from their policy which prohibited users from making free voice calls over the 3G wireless data network.
This means that providing you have a data-plan on your iPhone 3G/3GS you will be able to make the most of VoIP services on your iPhone, customers could benefit with lower monthly bills thanks to this.
Fring is one of the most popular VoIP apps for iPhone, however prior to this change in restrictions it was limited to WiFi connected handsets, Fring have officially announced that their “iPhone app is now completely functional over a AT&T’s 3G network”.
For more information check out IntoMobile. What is your preferred VoIP app for iPhone?
Also See: iOS 9 beta 6 likely for testing partners