Probably do have permission...
"Microsoft had no permission to change the OS on a machine, which amounts to unauthorised access."
Uncertain. If you are using Windows 7, 8, or 10, have you actually read the license? Some of the terms are quite heinous. My recollection is that the license gives them the right to modify the software on the system in any way they see fit, with or without notice, and they disclaim the software actually being able to do anything.
That said, the fact that they would keep hassling people over and over to upgrade (not a "never ask again option") I *do* hope they get the book thrown at them.
Biting the hand that feeds IT
