This happened to me too at some point. I contacted Spotify support, who, to my surprise, actually answered me (kudos for that, at least). The answer was bewilde

This happened to me too at some point. I contacted Spotify support, who, to my surprise, actually answered me (kudos for that, at least). The answer was bewildering though: apparently this can happen(!?!) in the web player! Not having time to get into a fight, I just bit the bullet and spun up their dedicated client app in a VM (no way I trust that monster to run wild on my computer). That got rid of the ads for me. Overall, I share the sentiment that so many people in this thread express: Spotify is slowly getting worse and worse. A shame. But luckily it's not outright terrible yet, i.e. we're not outright at "pay us, and we'll show ads down your ears". Yet.