Have you tried powering off the phone and powering it back on again? Have you tried a factory reset?
A factory reset will turn the phone back into factory settings to when you first purchased it. If the issue is software related then this will fix the issue.
On the home screen, touch the gear icon(flower looking icon)
Under ALL touch Backup and Reset
Touch Factory data reset then Reset phone then Reset phone
Were you able to follow my steps and complete them?