How to Reset a Network on the iPhone
Reset your iPhone's network connections to clear any access points and connection settings associated with the device. Access points, or Wi-Fi networks, provide a way for users to connect to the Internet through various devices, like computers and mobile phones. Completing a reset on the iPhone's network settings may also help you repair connection issues you are experiencing with the device. Resetting your iPhone's network connections will clear all saved access points, network settings and preferences from the device.
Tap the "Settings" icon on your home screen.
Select "General" from the Settings page.
Scroll to bottom of the General menu. Tap the "Reset" tab. The Reset screen opens.
Select the "Reset Network Settings" button. A warning message appears. Tap the "Reset Network Settings" button of the warning prompt to execute the reset. Tap the "Cancel" button to abandon the reset and return to the Reset screen.