Motherboard? Anyway, if it has an imei, use the unlock portal. I suspect an unlock code is no longer available, though.

https://www.att.com/deviceunlock/

Hello @Paul Okoroafor we're happy to help with options to unlock your device.

In addition, to the information provided by @sandblaster. If you are planning to use your AT&T Device with another carrier, it has to be unlocked and meet the requirements listed below.  You'll also find information about why your request may have been denied. Here are the General Requirements for All Unlock Requests:

1. Go to our Device Unlock portal.
2. Select Yes if you are an AT&T Customer, No if you are not an AT&T customer. 
3. Enter your telephone # if you are an AT&T Customer. Enter your IMEI if you are a non-AT&T Customer.
4. Follow the prompts. 

If additional assistance is needed with your unlock request, to best serve you while out of the country; please call +1.314.925.6925 (free from device). We're here if you have any questions. Thank you for contacting AT&T Community Forums. 

Alasani, AT&T Community Specialist 

Thanks. I will try that.

Good day sir. I followed your direction and I got this mail:

Unfortunately I don't have the 8 digit unlock code, the only code that I now have is the above given to me and it longer than 8 digits, moreover, some of the description did not match my phone- eg: my phone is window 10 not 8.1. i didn't find AT&TAll access in windows start screen. I really don't know what to do.

Any help for me please?

Paul from Nigeria.

Hello @Paul Okoroafor  we'll be glad to provide you with detailed information on what the 8-Digit code is.  You can learn how to find it on our PUK Support page.

The 8 Digit code requested is the PUK  which stands for the Pin Unlock Key.  Follow these steps to access your 8 digit unlock code. 

1. Go to your account overview and open the My wireless section.
2. Scroll to My devices & add-ons and choose the device that needs a PUK code.
3. Select Manage my device.
4. Under See device options, select Get your PIN unlock key (PUK).

Keep in mind: If your device displays PUK2 or PUK blocked call operator, then the wrong PUK code was entered 10 or more times in a row. The SIM card is blocked and must be replaced. For additional support sign in to Troubleshoot & Resolve and select the device that needs the PUK code. 

• In addition, you can visit the AT&T AllAccess App  to Monitor data usage, set up alerts, and eliminate overages with AT&T AllAccess data monitoring tools. which requires an Android tablet, Windows 8.1 or higher, or a USB modem with AT&T mobile broadband.

In regard to the device you will need to contact your manufacturer if you have additional questions. While out of the country; please call +1.314.925.6925 (free from device). Thank you for reaching out to AT&T Community Forums.

Alasani, AT&T Community Specialist 

Thanks a lot. I will try it .

Thank you for your support so far. I am still having challenges. The PUK given to me by my service provider in Nigeria is not accepted. The device said that its wrong code. The reason I guess is because as I said in my first post, I have not used AT&T services in the device before because is not available in Nigeria. I don't even knew about the organization before until I got this problem. my phone motherboard got bad and I mistakenly bought online AT&T locked motherboard from eBay. That is how I landed into this problem. I can't send it back to the merchant because it had been fixed to my phone and I don't know if they will accept it back. Besides, the merchant did not ship to Nigeria, I bought it through a friend that lives in Texas who send it through a friend coming to Nigeria. It appears that I am helpless, that is why I opted for the forum may be God spirited person from the organization could help me.

Thank you for been there. Jehovah's blessings.

Paul