u/General_Bottle3300

Hi guys, some days ago i bought a Sony Xperia Z from 2013 for just 15 euros and i was thinking of putting a custom rom on it, but as soon as i checked if it was unlockable i saw it wasn't. I know very little of Sony's devices so if anyone can tell me if there's a way to set that to yes i would appreciate it also because the phone isn't carrier or network locked (i checked in the service settings). The model is C6603