Does upgrading iOS change my IMEI? Does upgrading iOS change my IMEI? I was told not by AT&amp;T not to remove my SIM card or certain restrictions that they had placed on the iPhone, at my request, would be lifted. I want to know if upgrading my iOS is like removing the SIM card. I think this was because the IMEI number changes when the SIM card is removed from the phone.

Does upgrading iOS change this number?
The IMEI is kind of like a MAC address for the cellular network only. It is nearly impossible to change it, you can only spoof it on a software level. So the answer is, No, your IMEI will never change unless you really really want it to. Removing the SIM card shouldn't change the IMEI either...