Okay well here's a quick one to bust some bubbles. I bought my HTC One via Wal-Mart on promotion in April. In June I figured to hell with At&t. With that being said I rooted the phone and got S off. Then found a mod on the Development fourm for the One that let me unlock the international menu. I bought a Net10 SIM Card at Best Buy. Cut the SIM to fit and BOOM!!!!!!!! No need for a UNlock code or any of that. Net10 gave me the apn info and from there I've been able bypass all the usual hassle.
Sent from my HTC One using xda app-developers app