Well, luckily, there is an easy fix in the form of two apps that almost do the same thing. And, yes, they are completely free.
The first is Never10. It's main feature is how simple it is to use. It's also a very small application. Download it here: https://www.grc.com/never10.htm
However, if you're not happy with Never10, you have the GWX Control Panel. It give you more options and can run in the background to monitor for any Windows 10 attempts at installing. Download GWX Control Panel here: http://ultimateoutsider.com/downloads/
There you go. An easy solution for an annoying problem.