How to erase and restore your iPhone

If your iPhone is FUBAR or you simply want to restore an already-activated phone from a backup, here's how to wipe it and bring it back to Apple's initial setup screen. Note: You'll lose all data on the iPhone that hasn't been transferred to iCloud Drive or another cloud-based service.

1. Launch the Settings
2. Tap General.
3. Tap Reset. It's all the way at the bottom.
4. Tap Erase All Content and Settings. You may have to re-enter your passcode to do so. Once you do this, the phone will erase itself, restart, and return to the setup screen.

Note : If you are not Tech Savvy or not sure/aware of technical stuffs, suggest you to contact your Technical Professionals @ 13 Tech to handle the situation and provide a solution.