If you're a new T-Mobile customer or you recently purchased a new phone, you may have a new SIM card you'll need to activate. Here's how to set it up.

If, on the other hand, your transferring a physical SIM to an eSIM on a completely different iPhone, here's how to do it.

AT&T is launching a new Account Lock feature that will let wireless customers prevent unauthorized changes to their account, such as phone number and SIM card transfers.