How or where can I unlock an ATT Lumia 1520 with fees unpaid?

[Walkerboy79]

I stupidly bought a Lumia 1520 off craigslist without meeting at a ATT store. It wasn't blacklisted, but when I went to the ATT device unlock portal...it showed fees unpaid!
I live in Canada and would like to unlock it for use here. Can anyone make a good recommendation for a website to unlock a phone like this?

Might be best to PM if you have an answer.