Faith said it was VOIP, and if it had not been the phone should still have worked plugged into the old filter. It certainly sounds as if voice service has been cut off.
Re: Windows 10 seems to have installed itself without my permission
Microsoft have been pushing Windows 19 as a "recommended update' which means that it will install itself automatically in most computers - you have to actively work to stop it.
The intent of making recommended updates automatic was to get important security updates installed quickly and a lot of people think that Microsoft are misusing the system in this case.