r/t unlocking abroad for use with another carrier

I am abroad and have an Iphone 7. I want to unlock it in order to use it with another carrier. I can't get into the ATT site, as it throws up "network difficulties," and we all know how easily found and great their customer service contact is to connect with. TIA

P.S. - My phone is legit with contract fulfilled, etc.. I am also currently NOT with ATT (have no account with them), as I am abroad.