Good new for those of you who accidentally upgraded your iPhone 3Gs to unlock unfriendly iPhone firmware 2.2.1, ModMyi people have come out with a way to downgrade baseband 2.30 to 2.28. It was all the default baseband upgrade that bricked your iPhones or doesn’t allow Yellowsn0w to unlock afterwards.
The iPhone Dev team did released an unlock tool to help iPhone 3G users upgrade to iPhone firmware 2.2.1 without upgrading the baseband of their devices, but the release came late for those who upgraded instantly without heeding the warning from the unlock experts.
The new downgrade tool from ModMyi is called pHaseBanDowngrader and would enable you to downgrade your device’s baseband modem to unlock friendly 2.28. The tool is supposed to be used at your own risks and is meant specifically for people who accidentally upgraded to iPhone firmware 2.2.1 and got their devices bricked. The devices should be running on bootloader 5.80 too to use this tool.
If you recently purchased iPhone 3G and want to unlock the device, you could well be out of luck as recently purchased iPhones run on bootloader version 5.9.
Download pHaseBanDowngrader here.
Follow the given instruction minutely to resurrect your iPhone.