Restarting the device might help you resolve any software issues that are preventing you from connecting to the Internet. Press and hold the Power (Sleep/Wake) button until the red slider appears to reset your device. To totally turn off your iPhone, drag the slider. Press and hold the Power button for a few seconds until the Apple logo shows.
Check your Wi-Fi settings.
Make that Wi-Fi is turned on and that your wireless network can be seen. Go to your phone to accomplish this. Wi-Fi may be found in the Settings menu. If required, toggle the Wi-Fi switch to enable the capability. To connect to a Wi-Fi network, touch the name of the network you wish to connect to. If you're required for a network passcode, type in the right Wi-Fi password to continue. You're already connected if you see the blue checkmark next to the network name.
Set the network settings to default.
Resetting the network settings restores the network settings to their factory defaults, removing any issues that may have arisen as a result of erroneous network configuration. However, network information like Wi-Fi networks and passwords, cellular settings, and VPN and APN settings you've previously used will be wiped as well.
