Every phone should be unlocked, that leads to independence from the carrier it is got with. However the process is connected to some tiring actions but unlocked phones have advantages above original ones, e.g. you can use any SIM and any network in the world.
However, now everything is easier with Ultrasn0w 1.2.4. That brings iPhone 4 and iPhone 3GS unlock on iOS5. Users who rely on unlock on iOS 4.*.* can now update to iOS 5. Steps below will help you to unlock your phone.
Firstly you need to jailbreak your iPhone 4/iPhone 3GS using Redns0w. If you have no idea how to jailbreak your phone, click here.
After jailbreak, head to Cydia -> Manage -> Sources;
Then tap on Edit and add the following repo: http://repo666.ultrasn0w.com
Hereupon, search for Ultrans0w in Cydia, tap on it and then install.
After this, you will get your iPhone4/iPhone3GS unlocked, hope you have not got any problem during the process. Now you can get more pleasure with your unlocked phone.