Had a similar issue with Win 10 nagware ( and a friend who had it installed without her specific , which took hours of my time to upgrade back to Win7 Pro so sent the following to the Microsoft UK contact point; had a phone call back within 30 mins - and it seems that even bits of their legal don't really understand what's going on.
FTAO Microsoft UK CEO: and Microsoft UK Legal,
Over the last few weeks and days my Win7 Pro based PC has been the subject of a number of unrequested and increasingly insistent attempts to install Win 10,. Since I have not requested that this software even be downloaded to the PC, I regard this as attempting to subvert the integrity of the current installation and data, which in my view classifies it as deliberate malware, and an action which is in direct contravention of UK law under the Computer Misuse Act 1990. Arguably, such activity may also contravene UK contract law in relation to obligations associated with the previous software purchase. Pls take this email as formal notification that should Win 10 install itself on this or any other computer system which I own or have responsibility for, without my specific and express permission, I will report this to both the Police and other appropriate UK Governmental; Agencies as a potentially criminal act by Microsoft. I will also seek via the UK courts legal redress and compensation for all time, costs, and other incurred charges associated with restoring the said computer systems to their original state. Pls be aware that should I wish to install Win 10, I am more than happy to pay for a full licence, but it will be at a time and date of my choosing, not that of Microsoft.
I hope that the above makes thing clear for you - I await your comments with interest.