Two ways to do it…
First (I've used this method in the past, works every time)
Call AT&T, tell them you are going overseas next week and ask them to unlock the phone. You'll get the instructions and be done in 15 minutes.
Second (variation on the first, courtesy of Mase Mase on XDA-Developers.com)
http://forum.xda-developers.co…..ostcount=4
* Power on without SIM
* Type in #7465625*638*
* A Dialog Box will appear. Enter your Unlock codeand press OK
* Device should say: “Successfully Disabled Locking Status” and press OK
* Your device has been unlocked.
*The 8 digit code can be obtained by calling AT&T Technical Support and given the representative the IMEI number. In exchange they will give you the Subsidy Unlock Code.
To obtain the IMEI number press *#06# on your mobile device.
Third (courtesy of _TB_TB_ on xda-developers.com)
http://forum.xda-developers.co…..p?t=465597
- type the following code in dialer *7465625*638*#
- enter valid MCC/MNC of any carrier (list: http://en.wikipedia.org/wiki/M…..twork_Code ; eg. 310038 for AT&T)
- As NCK, enter 12345678
- tap OK (it should tell that SIMLock enabled)
- type the following code in dialer: *#7465625#
– type the following code in dialer: #7465625*638*#
- enter code entered earlier (12345678)
(This is the process I used, visit xda-developers for details).