Go to the website to cancel it again, and be sure to delete your payment info. That will stop any future charges.
You should contact customer support through this link to tell them about what happened:
https://support.spotify.com/contact-spotify-support/
They'll help you out.
If you get an automated email directing you to the community or help pages, you need to reply directly to that email (even if its from no-reply) and one of the customer services agents will get back to you.