This iPhone bug disables phone numbers. Here’s what we know so far
To remove and replace a physical SIM card, all you’ll need is the SIM tool that came with your iPhone. This is a small pin tool, and it’s quite possible that you never took said tool out of its original box when you first bought the device. Either way, you might want to make sure you do this after you have a replacement SIM card in your possession to avoid any service interruptions.
Once you have a new physical SIM card in your possession, you need to know your phone’s EID number. Any T-Mobile representative will likely ask you for this information, and you can locate it by going to Settings -> General -> About on your iPhone. From there, scroll down the page to find your iPhone’s unique EID number, and a T-Mobile representative should be able to easily activate a new SIM card.
T-Mobile offers a set of troubleshooting instructions for those who are having trouble with their eSIM cards on various Apple devices, including the iPhone. T-Mobile suggests that you make sure your iPhone is updated to the latest version of iOS (currently 15.4.1) before trying to do anything with your physical SIM card or digital eSIM service. T-Mobile also suggests that you’ll need an unlocked phone or one purchased directly from T-Mobile.
Mark Gurman also reported via Twitter that you can delete your eSIM account and create a new account from scratch. This is a process you might want to do under the supervision of a T-Mobile representative, as there’s always a chance you could screw something up on the service side.