There’s two places you should double check. 

The first is your account settings on the Sonos website. Sign in, the go to My account, and select profile. Scroll down to Contact Options, and make sure both selections are unchecked. I’m somewhat paranoid, if they’re already unchecked, check them, wait a minute, then uncheck them.

Second, open your controller, and go to settings. Then app preferences, and scroll down to Allow pop up messages. Make sure that is off. Again, paranoia suggests if it’s already off, turn it on, wait a minute, then turn it back off. 

If you’re still getting pop up messages after that, take a screenshot of them, and post them in this forum, so Sonos knows exactly what messages you’re seeing.