[tsac]

Do a backup for your information first and try doing a factory reset then test the function. If it then works try adding back your contacts and other information then test again. If it still works then try adding back one at a time your apps you added to the phone. Hopefully the one causing the problem will be found if it is an app. If after the factory reset it does not work it may be hardware related but based on your comments it seems it may be a corrupted OS. You can try doing a reload with a clean copy of the OS then do some testing.