@cruzer-u3
ONLY if your have a current account OR purchased a commitment free iPhone from Apple, if you don't have an account with AT&T they will not unlock anymore, change in policy.
@Salty50
You have iOS 4.3.3 firmware on your phone.
All Cydia tels you is that you have the SHSH's/blobs for 5.1 saved.
You need SHSH's/blobs to upgrade to 5.0/5.01/5.1 firmwares as Apple is not signing those anymore, 5.1.1 you can upgrade now.
If you don't have SHSH's for 5.01 you cannot upgrade to 5.01 anymore.
With redsn0w you can upgrade to 5.1 using a custom made IPSW firmware file with your SHSH's stitched to it.
Siri is not an option on 4.3.3, it legally works on 5.01 but is not legal on 5.1 or 5.1.1 (Apple left the door open on 5.01

)
The jailbreak for 5.1.1 is only weeks away, just sit tight and keep checking this forum for a 5.1.1 untethered jailbreak. As soon as that is out upgrade to 5.1.1 and jailbeak your phone.
You can upgrade now and do an untethered Jailbreak for 5.1.1 but it will force you to have your phone connect to computer evertime you restart phone.
Just read up on Jailbreaking in this forum and you will learn soon enough.