You can try doing a factory reset. but you will lose all data on the phone if it has not been backed up.
If you go here:
it will give you a step by step as well.
If you have any other questions on this, just let me know and I'll help you in any way that I can. And before leaving this page, please use the rating box at the top to rate the answer at least 3 Stars/OK Service or better so that I receive credit for assisting you.