You won't be able to do so, your carrier/network requested this, and there isn't a way to do it; with that said, I've seen another thread with a different Xperia, were the carrier/network authorized their users to unlocked their bootloader, once they did so, they communicated with Sony so users could take their phones to an Xperia center and get it done, again this might not be the case but do contact your carrier/network, again this is something they, your carrier/network, requested.
