How to Reset the Software on an Android Phone
When all else fails, you can do the extreme thing and reset all software on your Android phone, essentially returning it to the state it was in when it arrived. Obviously, you should not perform this drastic step lightly. In fact, consider finding support before you start:
Open the Settings app.
Choose Backup & Reset.
On some Samsung phones, this item is found by choosing the General tab in the Settings app.
Choose Factory Data Reset.
Nothing scary happens yet.
Touch the Reset Phone or Reset Device button.
Still nothing scary.
Touch the Erase Everything or Delete All button to confirm.
Scary: All the information you’ve set or stored on the phone is purged.
Again, do not follow these steps unless you’re certain that they will fix the problem or you’re under orders to do so from someone in tech support.
You can, however, follow these directions should you decide to sell, give away, or return your phone. In that case, erasing all your personal information makes a lot of sense.