Fuzzyband is the favourite utility to downgrade your baseband because it does model checking, it downgrades all variations of baseband from 2.30.03 to four.26.08 (3.0 beta5), and reviews the present bootloader model on monitor.
Downgrade Your iPhone 3G Baseband Using Fuzzyband
Press to launch Cydia out of your SpringBoard.
Once it completes you will be displayed your Bootloader Version, your Baseband Version and your iPhone OS version.
Once the downgrade has completed successfully you will be displayed a Done! message saying, “I Haz Downgrade!” and you will be on the 2.28 baseband. That’s it for using fuzzyband to Downgrade Your iPhone 3G Baseband .