8. Use Volume buttons to scroll to Factory data reset, then press the Power button to select it.
Allow several seconds for the reset to complete.
9. Use Volume buttons to scroll to Reboot system now, then press the Power button to select it.
Allow several minutes for the reboot to complete. If the phone doesn't finish rebooting, press & hold 
the Power button until the screen turns dark, then release it to power up normally.
10. If you reset your phone because you suspect a third-party app is causing problems, when you set up the 
phone again, be sure you don't copy all apps. Restore one app at a time and use the phone for a while. 
If the phone has no issues, install the next app and retest.
Get more help
Issue Where to get help
Billing or cellular network issues Contact your carrier.
Learn to use an app
Open the app and touch   or   > Help.
Phone issue Visit mobilesupport.lenovo.com for solutions, user forums, live contact 
options.
Fix issues : Maintenance procedures 248