Hi @am.gear3
Welcome to the Sonos Community!
If you are using the Sonos app to initiate playback, and if the only Spotify account added to Sonos is a paid account, you should not be hearing ads. If more than one account has been added, be sure to only use a paid account when selecting music to play.
If, however, a Spotify app is initiating playback, then that Spotify app must be logged into a paid account to avoid ads.
And if a Voice Assistant is being used to initiate playback, on the other hand, please ensure that the same paid Spotify account that’s been added to Sonos is added to the VA, and that it is selected as the default.
I hope this helps.