I'll share my experience too.
I called two days ago at around 11am. Dialed 1-800-331-0500, pushed 1, pushed 0, talked to a guy and told him that I needed to unlock my iPhone. I
do not have an ATT account. I told him my aunt from abroad gave me this phone because she discovered it was locked to ATT. The guy asked for my name, email, IMEI, and my aunt's name (wtf?) and created a ticket. He said I would receive an email within 5-7 days.
Today, at around 10:30am, I decided to just try the chat approach. I talked to a very friendly rep, after waiting 20-30 minutes?
Anna: Can I confirm the wireless number that we will be working with is?
me: I do not currently have an ATT account; I am actually wondering if it is possible to get an iPhone 4 unlocked; it was purchased off Craigslist and I will be studying abroad this summer.
Anna: I'll be more than happy to assist you, one moment please.
Anna: May I get the IMEI number please? You can access this by dialing *#06#.
She asked for my IMEI and my email address.
Anna: The request was processed successfully. You will receive an email with the steps to restore as new device with iTunes. The unlock will not be completed until you complete the process with iTunes. This can take up to 72 hours after restoring via iTunes.
...
me: So I should wait for an email from ATT then?
Anna: Yes, you will receive the email with the steps to restore via iTunes.
Anna: Once the restore is complete it can take up to 72 hours.
me: So I restore first and then wait for an unlock?
Anna: Yes. It is similar to the iPhone activation process & can take up to 72 hours due to the amount of requests at this time.
Immediately after the chat, I received an email from ATT linking to the PDF others have posted where ATT says:
We have reviewed your request and confirmed that you are eligible to have the requested iPhone unlocked.
To complete the unlock, simply...
I gave it some time, came home and decided to try it out at 9:30pm. Took my Gevey SIM out, put just my Tmobile SIM in the phone. DFU'd my iPhone and deactivated it with redsn0w.
Rebooted it, shows the activation screen. I opened up iTunes and it told me I had a passcode and needed to enter it. I left it at the activation screen and went "oh sh-t, did I have to disable that?"
I swiped to unlock and breathed a sigh of relief as I just entered my passcode. Restarted iTunes, and pops up with the
beautiful Congratulations screen.
I will consider doing this for my old 3GS, although it is jailbroken and has ultrasn0w...probably will not? I dunno. I will also try this for my friend's iPhone.
Some "background info":
-this iPhone has been active on ATT...I bought this on craigslist and the person had this device on her ATT account at the time (this was around August 2011)
-I received no case number for both the phone call and chat; I received no follow-up emails after the phone call
-I used the chat link that other MR users have posted because normally chat can only be accessed after logging into your ATT account; ATT uses a third party chat system, so you can technically just click that link and be connected
I will try again sometime this or next week to see if I can get my old 3GS or my friend's iP4 unlocked. I am not going to say for sure that the chat works best, but in my
one device, chat worked much quicker.