If your phone is old enough you can just get it unlocked by AT&T (Assuming that you reside in the US. If not, contact your service provider).
I believe Gevey SIM is the only way to unlock your iPhone for the moment.
A Gevey sim does not work for that baseband.
I have found an alternate way!
This allows you to unlock ANY iPhone model, any iOS version and any baseband.
http://www.unlockanyiphone.net/
Have you researched a carrier unlock ?
unlock your phone with SAM it's easy it's free and it doesn't eat up battery like that gevey chinesse crap
for a tutorial go to iclarified.com
you need a jailbroken iPhone no matter which baseband it is
Yeah, but SAM requires 5.x.x. If the OP doesn't have the blobs and tickets saved, the OP has to use tethered 5.1.
Check Applenberry site, they have Gevey that unlock all basebands. 50 bucks.