They are getting sneaky now trying to push the upgrade as a recommended update. And the dialogue box is tricky as well.
It has an OK button. If you close it with the X, it is the same as pressing OK. You have to find the link in the dialogue box to change or stop the upgrade. Sneaky, yes.
Even Paul Thurrott, a windows evangelist says it is out of control.
So, to stop the BS, I suggest Never10 from Security dude extraordinaire, Steve Gibson. Small simple app that will block the Windows 10 update and if the files have already downloaded, it will clean those up as well. Does not have to be installed, just run it and you can ensure your system avoids Windows 10.
You can grab it here: https://www.grc.com/never10.htm









