Network Unlock Code for Surface Duo is INCORRECT

At&t has one unlock code based on the IMEI you gave them.   If the code is not right, you have 2 options. 

The free option:  file an FCC complaint which would be forwarded back to AT&T upper management and they will contact you. Hopefully they can review the unlock request, confirm your IMEI, and double-check the provided unlock code to see if it matches their records. If it does this is a dead end for you.

The not free option:  pay an  unlock service to provide you with the full unlock set of codes which will include codes that AT&T does not have like the mck code which is the master code if you have permanently locked your phone to AT&T by entering the incorrect number too often.

I tried the not free option to no avail, have you any other suggestions?

Has anyone directly linked to AT&T seen this post and could provide assistance? 

I gave you the other option already 

🤨

If there was a 3rd option, I would have posted it. 

No one from here is any different than the AT&T support you already contacted. 

How do I file a FCC complaint?

This is why Google exists.   You asked how to file an FCC complaint 9 hours ago. If you had Googled it you would have had the answer 8 hours and 59 minutes ago.  And you would have had your complaint filed 8 hours and 55 minutes ago

If you had read the thread correctly you would have known that I am from the UK, it’s not possible to raise a FCC complaint. Our postcodes (zip code) and telephone numbers are not recognised by FCC. 

You are correct, the FCC will not respond via phone if you are outside the United States.

Pay an unlock service.