Hello there!
Thanks for reaching out. Hopefully I can help you out. I’d recommend having a quick scan of the email accounts you own for emails from ‘hello@spotify.com’. That way you can determine which one you used to sign up for Spotify. I'd also recommend checking out this Support article for more help.
If you were able to find your account, you can then follow these steps to cancel you Premium subscription.
Let me know how it goes!
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