My iPhone has frozen what do I do?

Restart 
Try restarting your iPhone. To turn off, press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off .

To turn on, press and hold the Sleep/Wake button until the Apple logo appears. 
If the screen appears frozen, try pressing and holding the Home button for a few seconds to close a frozen application and then try restarting again. 

Reset 
Press and hold the Sleep/Wake button and the Home button at the same time until you see the Apple logo. 

Remove Content 
Connect your iPhone via the USB and use iTunes to change the sync settings. Click on iPhone in the 'Source' list and select each tab to change the and then click 'apply'.

Reset Settings 
Tap Settings > General > Reset > Reset All Settings

Note: This will reset all settings. No data or media will be deleted. 

If the issue persists try erasing all settings. 
Tap Settings > General > Reset > Erase All Contents and Settings

Note: This will delete all media and data. All settings will be reset.