Just download spirit Jailbreak. Jailbreak the iphone and than add repo666.ultrasn0w.com in you cydia and simply download ultrasn0w reboot and your phone is unlocked

go to jailbreakme.com from your iphone and swipe. Unlock complete. youtube jailbreakme.com other wise use ultrasnow to jailbreak.read more here http://blog.iphone-dev.org/ or the link is blocked http://blog.iphone-devdotorg/ replace dot with .

the easiest thing to do is go to www.jailbreakme.com in your safari from the iphone and scroll jail break ...u will have cydia in the iphone. In cydia add the repository repo666.ultrasn0w.com to unlock the phone (make sure to turn off 3gs if u are going to use with T-mobile after jilbreaking) its a piece of cake these days....let us know if any confusion :)

I haven't used the Firmware to Unlock the I-Phone 3GS ,I used the remote unlock service to unlock the I-Phone from the Network lock,that is easy and best way to Unlock,I got the remote I-Phone Unlock service from here Unlocking4u and Unlocked successfully.....Remote Unlock service is best than all other Unlocking method....