Once your iPhone is disabled, you are out of options. Your only choice is to restore it to new condition.
Connect the iPhone to a computer with the latest version of iTunes running. This means to use a genuine Apple Lightning cord and connect the phone to a USB port on the computer. The computer will have iTunes version 12.5 or later running. You can locate the version number on the computer by clicking on the iTunes menu (top left) and choosing 'about iTunes'. On a Windows computer, you'd choose Help and then About.*
Hold down the power button and the home button on the phone:
> keep holding - the screen will go dark
> keep holding - the Apple appears and then disappears
> keep holding - the iTunes logo with the cord appears on the phone screen
> let go - Once the iTunes logo is on the screen of the iPhone, you can let go of the buttons.
There is a prompt on the computer screen that says there is something wrong with the iPhone.
On the computer, select Restore and follow the prompts. This will erase the iPhone, and you will lose all of your content and settings.
The iPhone will be ready when it says hello on the iPhone screen.
*If the iTunes version is older than 12.5, go to http://www.itunes.com and choose the Download button to download the latest version. Install it before starting to restore the phone.