Factory resets, also known as “wiping” or “data wiping” can help troubleshoot minor software issues in your iPhone.
Performing a factory reset will wipe your device clean of all personal settings and data. This can be helpful if you are experiencing software issues. It is recommended that you perform a factory reset before giving your iPhone to someone else so that they cannot see your sensitive personal data.
If you are troubleshooting your iPhone, please make sure you have a backup before initiating a factory reset.
How to backup your iPhone/iPad
Connect your iPhone or iPad to your computer. Unlock it and wait for it to show up on iTunes. Your settings are most likely are configured to automatically backup your device but it's best to manually backup your device to your computer just in case.
How to perform a factory reset from your iPhone/iPad
Method 1 - From your iPhone/iPad
Method 2 - From your iTunes
Open iTunes on your computer or laptop. (Link to download latest iTunes)
Connect your Apple device to your computer.
Select your [device] when it appears in iTunes.
In the Summary panel, click Restore [device].
If you are still having issues factory resetting your device, feel free to check out Apple's official instructions on restore your device back to factory settings.