Many people (myself included) went ahead and upgraded to Firmware 3.0.1 without thinking twice. Unfortunately, if you don’t have a data plan and you’re working with a phone that has been jailbroken, you’re going to need to reactivate your phone again. Currently, there are no fixes for redsn0w to address this, so consider this my tutorial.  NOTE: I have provided links all software, firmware, and bootloaders in the how-to below. Additionally this tutorial applies to iPhones that are already jailbroken and are currently running firmware 3.0

First, download the latest version of redsn0w. After you’ve done this, proceed as follows:

1.) Make a backup of your phone.
2.) Install firmware 3.0.1
3.) Download firmware 3.0 and bootloaders 3.9 and 4.6
4.) Use redsn0w to patch firmware 3.0 (select “unlock” and “cydia” only)
5.) Reboot your iPhone and let iTunes restore your data from a backup.

Success! In the process of restoring your contacts, photos, and apps, iTunes will automatically upgrade your firmware to 3.0.1 (previously downloaded) and you will not have to worry about jailbreaking your iPhone again because the original jailbreak remains intact.