AT&T has a whitelist system, they check IMEIs often and if your device is not approved, cell service stops working.

For Verizon, you have to call customer service to do a manual override.

Only T-Mobile allows any phone to work without explicit approval.

I heard that Australia now has a Nationwide whitelist system that even block unapproved phones from calling the emergency number.

Technology is really getting enshittified. 😓