Cellphone users like me change their carrier frequently. But with locked phone it becomes headache. You need to unlock the phone to use it with different carriers. Now there is one good news for Samsung Galaxy S users. A member from XDA forum devloped an appliction to unlock your device. Currently this application is in testing stage.
As per the application devloper, the application can work on Galaxy S as well as on other similar models of Samsung Android based cellphones.
Requirement:
In order to run the app, you’ll need to be rooted with BusyBox and have an active internet connection
Instruction to run the application:
- Download the application from here
- Run the application and follow on screen stps
- Save your /efs folder
- You will get a blank screen, this means the app can unlock your phone.
- Built .nv_data.bak once the phone restart
If you face any problem in unlocking you need to restore /efs folder saved on step 1. To do so start the application again and select restore option.
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Disclaimer : I am not promoting this application, neither unlocking the cellphone. Use this application at your own risk. Techienote or non of its member will be liable if the application do not work for you.
My name is Vidyadhar Sarmalkar & I work as a consultant and have done RHCE & CCNA. 
Here Is the full step by step tutorial on how to unlock Samsung galaxy S i9000 http://www.sh-phons.com/?p=113