O2 text you. But you must actually unlock it after in iTunes. The best way is to turn your device off, then put in a different network's sim. Connect iphone to computer with iTunes. Phone turns itself on and will then look to authorise the sim, iTunes will then say 'your iphone has been unlocked'... At that point you are now 'actually' unlocked. You can go back and put your o2 sim back in now.
After doing that.. THen use spirit. It will remain unlocked.