I know this may sound very mundane but i had to get this cleared. When a new iphone is bought i understand how it can be locked to a particular network. after jailbreaking it can be unlocked to work with other networks as well. but what i fail to understand is: when an iphone is restored or updated to a new OS why do we need the original carrier sim to activate the phone. how does itunes recognise which is the original carrier sim to activate the phone? could someone kindly shed some light on this matter please or direct me to where i can find answers to this. I do apologise if this has been asked earlier and I am repeating.