Spotify automatically switched to an increased subscription without an email. What can I do?

Hello, I had a discounted Spotify Student subscription.

Now my subscription has been automatically upgraded to Premium, and a higher amount has simply been debited. WITHOUT any prior notification via email.

Spotify's website says:
"Approximately 4 weeks before expiration, you will receive an email with instructions on how to renew your subscription and reconfirm your eligibility via SheerID."

However, I have not received any such email, not even in my spam.

What can I do now? How should I proceed?
Thank you and best regards