Log in to your Spotify account from the browser and go to the Spotify support page.Once you’re downgraded to a free plan, here’s how you can permanently delete your Spotify account: If you’ve canceled it already, wait until your benefits expire. To delete your Spotify account, you’ll have to wait until you’re downgraded to a Free plan by canceling your Premium subscription first. How do I delete my Spotify Premium account?
Spotify can also assist you if you’re unsure about what third-party app you signed up on to avail their Premium plans.