Finally the iPhone Dev-Team has released the PwnageTool 3.1.5 for Mac OS X which can be used to jailbreak iPhone OS 3.1.3 on iPhone 2G, iPhone 3G, iPhone 3GS (older bootrom) and iPod Touch 1G and iPod Touch 2G non-MC model. The latest PwnageTool 3.1.5 allows you to update your iPhone Firmware without changing the baseband. If you had already upgraded your iPhone 3GS to 3.1.3 firmware, then your baseband will be upgraded from 04.26.08 or 5.11.04 to 05.12.01 and the baseband cannot be unlocked.
So if you are a Mac user, you can download PwnageTool 3.1.5 to upgrade the firmware of your iPod or iPod Touch to 3.1.3 without changing the baseband. After you had successfully jailbroken your iPhone, you can use ultrasn0w to unlock it so that you can use a sim of your choice.
Source:http://www.techhail.com/iphone/
