Factory Unlock AT&T iPhone 4 & 3GS And Keep Jailbreak untethered
 

how it's possbile ?

unlock request only when you connect a Deactivated iPhone to iTunes , an interaction beetwen your iPhone with Apple server required to unlock your iPhone . so currently alot of people jailbroken their 5.0.1 in waiting a software ( Ultrasn0w ) unlocking solution or just profit to jailbreak liberty. so in this case if you are not informed that you can Deactivated your phone Without restore to 5.1 . sure you will off to untethered for a long moment .
Smart Mobility News: Factory Unlock AT&T iPhone 4 & 3GS And Keep Jailbreak untethered
Source :

Things you will need during this process:

Redsn0w o.9.10B6 (Download)

Step 1: Connect your iPhone 4 or iPhone 3GS with computer and launch latest version of redsn0w 0.9.10b6

http://cdn.howtoarena.com/wp-content...-jailbreak.png

Hold down both the Home button and the Power button for 10 seconds.
Release the Power button and continue holding the Home button until (approx 15-25 sec) your device’s screen turn black.

http://cdn.howtoarena.com/wp-content...-loosing-1.png

Step 3: Sit tight! Redsn0w will now detect your build

http://cdn.howtoarena.com/wp-content...ailbreak-2.png

Step 4: After successful detection of your iPhone’s build redsn0w will give you some options, check “Deactivate” and un-check all other options

http://cdn.howtoarena.com/wp-content...ailbreak-3.png

Step 6: Now eject your SIM try and turn off your iPhone
Step 7: Turn on your iPhone and connect it with iTunes and insert your SIM try
If everything goes well iTunes will give you an Unlock message.
That was it folks, you can factory unlock your iPhones while keeping your untethered jailbreak intact.

Source : Smart Mobility News: Factory Unlock AT&T iPhone 4 & 3GS And Keep Jailbreak untethered

you should do that before , need also lastest redsnow . ( answer to a mail )