SIM cards are small cards that contain the personal information that's stored on your cell phone. SIM stands for Subscriber Identity Module, and all phones on the Global System for Mobile Communications (GSM) network use these cards. SIM cards make transferring phones much easier, as you simply remove your card and slide it into the new phone, and all of your contacts and other personal data get transferred right over.

1. Sim Card Checker
2. Check My Sim Card Online
3. Sim Card Lookup

Sim Card Checker

The SIM card also helps your service provider connect your phone to their network. Remove the battery and place it aside. You will see the SIM card resting beneath where the battery was. The SIM card looks like a small card with a gold chip on the front. Avoid touching the gold chip. Take the SIM card out of the slot, gently removing any clips that are holing it in place.

Check My Sim Card Online

Turn the card over, and write down the number on the back. This is your SIM card number. Put the SIM card back in its slot gently, and secure it with the metal clips you removed while taking it out. Replace the battery, and slide the battery cover back in place. You can now power up your cell phone again.

Sim Card Lookup

I don’t think that the IMSI is generated with a Luhn checksum so I don’t think you can – but I could be mistaken. This is what I found about the format: The IMSI is a fixed 15-digit length.