To unlock your iPhone from its carrier, you'll likely need to contact your carrier directly to cancel your contract.
Tech Advisor on MSN
How to switch SIMs on iPhone, including eSIM
Changing physical SIM cards on your phone is always a fiddly business. First, you have to root for the little SIM tray tool ...
You can check to see if your iPhone is unlocked from a carrier using any of a few different methods.
Some results have been hidden because they may be inaccessible to you
Show inaccessible results
Feedback