Thanks for reaching out to the Community about this.
Hope you don't mind us replying in English as it's the Community's official language.
We suggest you first try updating the payment details in your Spotify account. Simply open this link and follow all the steps. Don't worry, you won't be charged additionally after you do this. It's just a mere confirmation of the payment details for your student discount.
Once you’ve done so, go to your account page and scroll down to Your plan - here you’ll see the updated price of your subscription.
Hope this helps. Keep us posted.
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“Music is the strongest form of magic.” Marilyn Manson