If your i Phone is running one of the baseband specified above you can successfully unlock your i Phone on the official i OS 5, 5.0.1 firmware.
Note: In order to update to the official i OS 5, 5.0.1 firmware and still preserve your baseband so it is unlockable, you will need to follow our in-depth how to guide using Red Sn0w.
Note: In case you are not familiar with Ultra Sn0w, it is a software unlock for your i Phone meaning you can use your i Phone with any carrier by simply inserting the SIM card.
Read through the description and tap the install button to install Ultra Sn0w 1.2.4 / 1.2.5 to your i Phone running i OS 5, 5.0.1.
Step 3: Once Cydia is up and running you will need to go into the Sources page.
To go into the Sources page tap Manage followed by Sources.
Update #1: This article has been updated which now includes the i Phone 4 ( baseband), i OS 5.0.1 firmware, and Ultra Sn0w 1.2.5.
Step 1: As we noted above you must already be running the official i OS 5, 5.0.1 firmware on your i Phone, and you must also be jailbroken on i OS 5/5.0.1.