> Second, I don’t think it’s related to the carrier or cellular provider Well you thought wrong. iPhone is very much a closed system with a lot of back end sec

> Second, I don’t think it’s related to the carrier or cellular provider Well you thought wrong. iPhone is very much a closed system with a lot of back end secret sauce to make the whole experience "just work". Carriers that officially support the iPhone get API access from Apple but Apple ultimately controls the devices. Things like SIM lock etc. are handled through Apple's servers. The carrier simply makes a request to Apple to unlock the phone. This is also how they enforce MDM for corporate phones. Reset a phone? First thing it does during the mandatory "activation" is check the serial number against any MDM policies to push onto the phone. And so on.