how can i unlock iphone 4g to any network?

First update to iOS 5.0.1 (the newest firmware).

Then jailbreak using Redsn0w 0.9.10 beta 3- http://www.chiphazard.com/2011/12/29/download-redsnow-0-9-10-beta-3-0-9-10b3-for-untethered-ios-5-0-1-jailbreak-mobilesubstrate-error-fix-direct-links/

In Cydia, you're going to search for "Ultrasn0w". This tweak unlocks your device.

there are many software available to unlock iphone and i unlocked it by remote unlocking..there are many online providers who provide the service..one of my friend got unlocked his iphone from Theunlockarena by remote unlock..and the important thing remote unlocking is available for some country and network providers only so if you are interested you can try from them before that see whether remote unlocking is available for your country and provider..