UNLOCK AN OUT OF CONTRACT IPHONE 5

I have been trying to unlock my out of contract iphone 5 since April this year. That was the same time that I did a Transfer of Service Responsibility and an upgrade to iphone 6splus (I used to be under my aunt's AT&T account). I was told by an AT&T customer service representative to do all the paperworks for this transfer in an AT&T branch because doing it online is not possible. When I went to Waldorf branch for the Transfer of Service Responsibility i asked them if they could unlock the iphone 5 and they insist that i do it online instead. I have been trying since then and have always been denied due to "WE'RE UNABLE TO PROCESS THIS REQUEST BECAUSE IT IS NOT A CONSUMER DEVICE". I have tried unlocking it with my aunt's account but was still denied with the same reason. I've called the consumer customer representative and was told that it was denied because I am not putting in the right numbers, which I strongly disagree. I've had this iphone since 2013 or 2014 so it can't be a contract issue. It was a refurbished model but I don't think this has something to do with the request. The model number varies though with what AT&T have and what i see on the settings. In other words, I am stuck. I am using the iphone 6splus now and I am sending the old iphone 5 to my home country soon. Can anyone help me with this one, PLEASE.