1: Please be sure you are using the factory ROM software.
2: Please be sure that the IMEI you get when typing in *#06# is the same as the IMEI under your battery. Likewise, it must be EXACTLY the same as the IMEI in your order.
Samsung Alternate Unlock Instructions:
1. Start the phone with non-accepted sim (click “Dismiss, and go to dialer), also make sure your Wifi is off.
2. In the phone dialer press *7465625*638*#
3. You will see a pop up window and in it enter the MMC/MNC code for the provider you want to use phone. (eg. 310260 for T-mobile USA, 310410 or 310380 for ATT)
You can find the list of codes here: http://en.wikipedia.org/wiki/Mobile_Network_Code
4. in CONTROL KEY field enter the Network Unlock code. Press OK and “Network Lock Successful” Message should appear.
5. Restart the phone.
If phone asks for unlock code again, input code and that should unlock it.
If this doesn’t work, please repeat steps without a SIM card.