Unlock code for galaxy s3 does not work

The non ATT Sim Card must be on a domestic provider and must be currently active. Otherwise it won't unblock. 

You would think that ATT might mention this.

Any help with same issue on Motorola Z2 Force?

This is an extremely old thread but I was wondering if the instructions mentioned above still work on new model phones. I have a Samsung J7 2018. This is what I am referring to:

"I was having the same problem with my S3. ATT has given me the same unlock code again and again. As a result of my extensive internet search, I found this and this worked for me. I unlocked my phone with the same unlock code given by ATT. Hope this would be helpful. 

Inset a NON ATT sim and switch on the phone.

When it prompts you to enter the unlock code, dismiss the unlock code screen.

a. Go to the Dial pad and dial *#197328640#

b. Please click on number [1] UMTS > [1] Debugging screen > [8] Phone Control > [6] NETWORK LOCK

c. You will see 3 options

d. Please click on number [1] Perso Sha256 INFO, the screen will change slightly

e. Please hit the MENU button then when the menu pops up please carefully hit BACK to return to the previous screen

f. Next Please click on number [2] Perso Sha256 ON, the screen will change again to a one line message

g. Restart the phone on the screen by holding the power button and click RESTART

h. When the phone prompts for the unlock code simply enter the unlock code provided to you

i. Your phone is now permanently unlocked!"

Thanks!

Hey there @Chacha_1, we'd be glad to provide you with the most updated unlock instructions for your Samsung J7 device.

First, you'll need to confirm that you've met all device unlock eligibility requirements:

• Your device:
  • Is an AT&T phone or device and isn’t active on another AT&T account.
  • Was paid in full when you bought it (not on an installment plan). You won’t have to wait 60 days to unlock it.
• Has a paid-off installment plan.
  • Paid through your monthly bill: Submit your unlock request at the start of your next bill period.
  • Paid off early: The wireless number assigned to the device must be active for at least 60 days. Wait 48 hours after you make your final payment to submit your unlock request. Learn how pay off your installment plan.
• Doesn’t have a past-due account balance. Make a payment to bring your account current. It will take 24 hours for your payment to post. 
• Hasn’t been reported as lost, stolen, or involved with fraud.
• Is an AT&T PREPAID phone that has had paid service for at least six months.

Next, you'll need to submit an unlock request through us online:

Heads up: You only get 5 tries to unlock your phone. After that, you won’t be able to use it with another service provider.

Feel free to reach back out and let us know how these detailed steps worked for you and thanks for trusting the community!

Lynn, AT&T Community Specialist