It can be hard to unplug it. I have a 2014 Samsung Smart TV. I didn't want the smart stuff but there wasn't much option. When I first got it I gave it my wifi password just to check it out, confirmed that I'd rather just use my HTPC and turned off wifi.
Lo and behold every few months something would happen which would make it clear that it was connected to the internet. I'd get banner ads. I'd get notices from the mothership about important updates. That sort of thing. Each time I'd discover that the wifi was back on and each time they'd have hidden how to remove it somewhere else.
Eventually I just changed my wifi password and that seemed to have done the trick.
Lo and behold every few months something would happen which would make it clear that it was connected to the internet. I'd get banner ads. I'd get notices from the mothership about important updates. That sort of thing. Each time I'd discover that the wifi was back on and each time they'd have hidden how to remove it somewhere else.
Eventually I just changed my wifi password and that seemed to have done the trick.