@teikwing

1. You need an Unactivated or Activated ATT Sim
2. Take out your T-Mobile SIM and Pop in your Unactivated ATT Sim card (Just found out any ATT Sim is ok).
3. Restore and Jailbreak with redsn0w (If you are already jailbroken and deleted wildcard_record.plist, you can skip this step)
4. Go to Settings -> General -> Network, and disable 3G
5. Let iTunes activate the phone - you should get a “Waiting for activation.” message, dismiss it and Open cydia.
6. Add the Ultrasn0w with source repo666.ultrasn0w.com
7. Install ultrasn0w and turn off your phone
8. Remove the ATT sim and insert your T-Mobile sim
9. Turn on the phone, once you receive service you should get the message. “iPhone has been activated”
You should gain signal bars and your push notifications should work. Remember to go into network settings and add your APN for your data plan. Test push notifications with the free version of the AIM app.

SSH to /var/root/Library/Lockdown/activation_records and delete wildcard_record.plist, the next time you reboot your phone, it will ask for activation again, thus allowing you to easily put in an AT&T sim and activate with iTunes open - this should allow you to skip the restore and re-jailbreaking steps if you already are in that state.
This will also fix the ultrasn0w signal losses. When you get signal losses after installing ultrasn0w, its probably because you restored an old backup of your phone which restored an older version of wildcard_record.plist. When you reset activation and use an AT&T sim, you gain push and a stable connection.

try to use this step to replace the 3rd step..

anyone..
im still looking for ori at&t sim please..