Terminated the contract but request to unlock phone is denied

I contacted AT&T at least 10 times before making a decision to terminate the contract, i.e. paying the Early Termination Fee and get the phone. Then I switched to GoPhone, so I'm now using PrePaid service. They all told me that I could unlock the phone online at www.att.com/deviceunlock. My requests were denied. 

Please tell me which option to choose from in the request form (current, previous, prepaid, Non-AT&T mobility customer) and what I can do to unlock the phone.

P.S. I need it unlocked since I'm from abroad.

Thanks.