T-Mobile: How to activate a new SIM card
If you purchased your device from T-Mobile, the SIM card is probably installed. If not, you must provide your phone's IMEI ...
Cricket Wireless: How to activate a SIM card or eSIM
Verify the ICCID and IMEI numbers. The ICCID is a serial number (up to 22 numbers) that identifies a SIM card. The number is ...