AT&T unlock device

Hi I purchased 2 phones from Amazon that were with carrier AT&T. I paid full price, but I am receiving a message that says 

'It looks like your device is on an installment plan and you haven’t paid it off yet. Follow these steps to pay off your installment plan early. Then, wait 48 hours before you submit a new request. If you pay off your device as part of your regular bill, you’ll need to wait until the start of your next bill period.'

I am in my country, Bolivia, and I can't unlock them on the AT&T webpage. I have read before it was 40 dollars to unlock it but it is not allowing me.