Back up your important data
Charge the phone to at least 50%
Open Settings
Tap Additional Settings
Tap Backup and Reset
Tap Erase All Data
Tap Reset Phone
Enter your lock screen password or PIN if prompted
Tap Erase Everything
Wait for the phone to restart and complete the reset
If the phone is unresponsive, turn it off
Press and hold Power and Volume Down together until recovery mode appears
Select Wipe data/factory reset
Confirm the reset
Select Reboot system now