Skype is available in App Store most 3G networks should support Skype presence and chat. However, Skype calling is not possible via the iPhone 3G Network you mest be logged on to WiFi Zone. Because Apple did not allow use Skype over the more prevalent 3G network, limiting itself to WiFi only even though 3G had the necessary throughput for it. Apple claimed this restriction was imposed simply because it was a carrier-dependent decision since transferring data over the 3G could be costly for carrier.So If you wants to use Skype, Fring or Truphone like apps over 3G, EDGE or GPRS you need to remove this restriction yourself, you need to first jailbreak your iPhone. Once that’s done, it’s a simple matter of installing from Cydia the “voipover3g” app. That’s it, simple as that. Note that this works for other VOIP programs as well, not just Skype. “voipover3g” app uses MobileSubstrate Library tricks apps into thinking that they are on WiFi even though they are on 3G/EDGE/GPRS. In the default settings you can use Fring, Truphone and Skype.
How to Install voipover3g.app using Cydia Step by Step Visual Guide :
Step 1 :
Press to launch Cydia from the SpringBoard.
In Search Bar type VoIPover3G and the App will popped up.
Step 4 :
Tab the Install button on the top right hand corner.
Step 5 :
Now tap the Confirm button to make sure the package download and installation.
Once the installation finished fire the Skype and make a call no matters whether you are on 3G, Edge or GPRS. Check the following screenshots of my installation and operation of Skype over my Edge connection on iPhone 2G.