The Apple iPhone is a powerful "smart phone" capable of a wide range of Internet-based functions, including web browsing, email and multimedia-rich applications. At its root, however, the iPhone is a phone and doesn't need any of these additional features to function as such. This being said, your carrier may prevent you from removing cellular data from your service plan.
The iPhone is capable of high-speed Internet browsing, email access and using a wide range of mobile applications, which usually involve a subscription to a cellular data package through your wireless provider. With a data plan enabled, you can access Internet-based functions on your iPhone wherever a wireless signal is available -- and as is the case with phone calls, the speed of your Internet connection may slow or even stop if reception is poor.
When your cellular data network is unavailable -- or, if you happen not to have one -- it's still possible to access the Internet using your iPhone. The phone has a built-in wireless adapter, much like the ones you find in laptop computers, capable of connecting to available wireless networks. To activate your wireless adapter, tap the "Settings button, scroll down to "Wi-Fi" and tap the gray "Off" button located next to it. A list of available networks appears on the screen.
iPhone Without Internet
Of course, you don't need Internet at all to use your iPhone. Without an Internet connection, your iPhone is capable not only of making calls and sending text messages, but also viewing pictures and videos you've saved on it, playing music through its iPod media player and using applications that don't require the Internet, such as "Notes" and "Calculator." Internet enhances an iPhone's functionality, but isn't essential to its operation, from a functionality perspective.
Although it's possible to use an iPhone without a cellular data plan, neither of the two U.S. carriers who officially provide support for the device -- AT&T and Verizon Wireless, as of April 2011 -- permit you to use an iPhone on their networks without purchasing a data plan. If you purchased your iPhone unlocked -- or if you unlock it yourself, a process both Apple and iPhone carriers frown upon -- you can use it with another carrier and, therefore, without a data plan.