Certain iPhone functions, such as web browsing, can be utilized without a data plan if the user has access to a wireless signal. However, most wireless carriers do not allow iPhones to function as cell phones over their networks unless the user subscribes to a data plan.
Without a data plan, an iPhone functions similarly to an iPod Touch. The user can access apps, surf the web and check email as long as Wi-Fi access is available. Some texting apps, such as iMessage, also function over Wi-Fi. The phone cannot be used to make calls over a wireless carrier's network without a data plan, although some third-party apps can mimic this function.