If you have an older generation iPhone that you're no longer using, or simply looking to change cellphone carriers, you may have an iPhone without a SIM card that you aren't sure what to do with. These iPhones can always be reactivated with a new SIM card and cellular account, or they can be used strictly as an iPod Touch for music, applications and Wi-Fi web browsing.
IPhones that don't have a SIM card certainly aren't destined for the trash heap. Apple allows iPhone owners to continue using their devices after their contracts have been canceled or expired as an iPod Touch. These unused phones can be given away or used as separate music players -- a particularly useful option for individuals who have extensive music collections.
If you have an original iPhone without a SIM card, you'll find that it is essentially useless. Although Apple allows you to use the original iPhone as an iPod Touch, the original SIM card must be left in place. Without the SIM card, Apple advises users to contact their cell phone carriers for a replacement. This SIM card allows you to activate and restore your iPhone regardless of whether it is currently active. When used in this fashion, you'll have access to all your iPhone's features except calling, text messaging and the 3G network.
iPhone 3G and 3GS
If you have an iPhone 3G or 3GS, you will not need a SIM card to continue using the device. Once the iPhone is activated, you can remove the SIM card and use the device strictly as an iPod Touch for music and applications. If you have access to a Wi-Fi network, you'll also be able to browse the Internet and download purchases from both iTunes and the mobile App Store.
The major limitations of using your iPhone as an iPod Touch are the inability to make phone calls, send text messages or access the phone's 3G network for mobile Web browsing and downloads. To browse the Internet, stream media to your phone or purchase music and applications, you'll need access to a Wi-Fi network.