Earlier the Dev Team warned the iPhone users not to upgrade their iPhone to 3.1.3, to preserve their broadband and wait till the next version of Pwnage Tool. The reason behind this is that upgrading to 3.1.3 with Ultrasn0w/Blacksn0w will caused the iPhone users lose their unlock and will unable to get it back. The OS 3.1.3 has baseband 05.12.01 BB for iPhone 3G/3GS, and its firmware is not down gradable. Here is a guide through whom you can downgrade your iPhone, if you have updated iPhone 2G, 3G or 3GS to OS 3.1. One thing that should be remembered is that only firmware can be down gradable and not the baseband.
