Downgrade iPhone 3.1.3 Baseband 05.12.01 to 04.26.08 to
 

Let me clear this upfront. The following instructions will only help downgrade iPhone 3G which is currently on iPhone OS 3.1.3 with 05.12.01 baseband and older bootloader 05.08. This wont work with iPhone 3GS.

http://www.redmondpie.com/wp-content...Fuzzyband1.jpg

If your iPhone meets the above criteria, you can then use the latest version of Fuzzyband which supports iPhone 3.1.3 to downgrade your 05.12.01 baseband to the older 04.26.08 even if you accidently upgraded to the stock iPhone OS 3.1.3 from iTunes. Once you have downgraded your baseband, you can then use ultrasn0w to unlock your iPhone on iPhone 3.1.3 firmware. Here’s how you do it.

Step 1: To downgrade your baseband from 05.12.01 to 04.26.08, you must first jailbreak your iPhone 3G running firmware 3.1.3 by using any of one these guides: redsn0w 0.9.3, redsn0w 0.9.4, sn0wbreeze or PwnageTool 3.1.5.

Step 2: After you have jailbroken your iPhone, Go to “Cydia” on your iPhone and Search for “Fuzzyband” and then install this application.

http://www.redmondpie.com/wp-content...Fuzzyband2.png

Step 3: Start “Fuzzyband” app and touch on “Downgrade” button to downgrade your Baseband from 05.12.01 to 04.26.08.

http://www.redmondpie.com/wp-content.../Fuzzyband.png

Step 4: You should now be able to perfectly unlock your iPhone 3G using the latest version of ultrasn0w by following the step-by-step guide posted here.

NOTE: For those of you who don’t know your bootloader, simply run Fuzzyband and it will report the version number for you.

NOTE: For those of you who don’t know your bootloader, simply run Fuzzyband and it will report the version number for you.

upgraded version of Fuzzyband (Baseband downgrader). Technically, iPhone 3G can now be unlocked on iphone 3.1.3 baseband 04.26.08 with ultrasnow
http://www.redmondpie.com/wp-content...kiPhone4.0.jpg
NOTE: I haven’t tested this on my iPhone 3G. This is only for iPhone 3G with 05.08 bootloader. Proceed only at your own risk