As part of a cleaning process for my iPhone 6, I like to do an Erase all content and settings reset, and start from scratch from time to time. However, since I activated this phone for the first time, I've switched carriers (and therefore SIM cards) twice, (from EE, to giffgaff, to Three). I've done a full reset on my iPhone 4 (activated on the same SIM, the EE one) and tried to activate it with the giffgaff one, and it didn't work. I'm assuming the same thing will happen with the iPhone 6? I'm running iOS 9.3.2, and everything else is up to date. If the same thing would happen, what can I do to make it activate on the Three SIM? Would I have to take it to EE and get them to unlock it? (I've tried jail breaking before, it's never worked for me )-: )