If you contact at&t and inform them you wish to unlock your Samsung Black Jack too, they will happily provide you with the unlock code provided you have been with them for mover 3 months, or if you paid full price for the phone.

However the instructions at&t gives you are incorrect.

at&t will provide you with the following instructions:

1 Power off device and remove the AT&T SIM card.
2 Power on the handset.
3 Enter: # 7 4 6 5 6 2 5 * 6 3 8 *
4 At the Network Lock Screen, enter the Unlock Code and press the left soft key (LSK) Ok.

That above is incorrect, the correct way is:

1 Power off device and remove the AT&T SIM card.
2 Insert non AT&T Sim Card and Power on Device
3 Enter: Unlock code at Network Lock Screen
4 Click the left soft ky (LSK) Ok

From conversations with Samsung I have been told that at&t was informed to changed the instructions when the BlackJack II first came out but at&t has yet to do so. Maybe because they want to lock you into their network forever.