A subscriber identity module card allows you to use cell phone and data service on your iPhone; it contains information about your account and identifies you as a user of a specific network. Many phone service providers require the SIM card number for support calls or number transfers. If you're not prepared, it can be frustrating to hang up, take out the card, and call the company back. By finding the number without removing your SIM card, you can save yourself hassle and frustration.

Using the "About" Screen

Your iPhone's "About" screen contains a great deal of information about your phone, including the SIM card number. Tap on the "Settings" button, choose "General," and tap on "About." Scroll down the page until you find the field labeled "ICCID." This is your SIM card number.