How can I completely erase all personal data from / reset my iPhone?
You may need to wipe your iPhone in order to sell it or get the device serviced or replaced. After all, the iPhone is a treasure trove of personal data with access to contacts, online accounts, and more.
To erase your personal data from the iPhone follow these steps:
1. Sync your iPhone with iTunes to back up your data for future use
2. Navigate to Settings -> General -> Reset
3. To reset all settings to factory defaults without deleting your music, contacts, etc. choose "Reset All Settings"
4. For a complete wipe of all personal data from the iPhone select "Erase All Content and Settings"
5. Confirm your selection when prompted