hi i'll try to help here i think what you need is the carrier lock code(a chunk of memory set a side to protect the firmware/ui) or a program that hacks the values. as far these go one is the hard way and the other is the easy. the good(some what easy way) : call the carrier ask them for the lock code (may have to go through many steps to get unlocked) if you in good standing they may be friendly and let you have it and the steps to get there. the bad(some what hard way) : "program or script hack" as this step leaves out the carrier and might get you a hacked "carrier free"(aka jailbreak) phone. not all phones have a big fallowing and most phones get left behind for this type of carrier unlock and a chance at brickng your phone. side note some report network loss/unstable or unstable phones after unlocking . "at your own risk".
i hope i wasn't to adhd for this reply