Thanks for reaching out to us and welcome to the Community 🙂
Hope you don't mind us replying in English as it's the Community's official language.
Can you head here and check if the student discount is activated? If it is but you've been charged more than expected, we'd suggest you give these steps a go so you can make sure you don't have a secondary account.
If you can see in the receipts that you've been charged for a Premium subscription, you can click here and try again activating the student discount. After you've been verified by SheerID, you should receive an email with a link for activation. Click on the link to activate the offer. The last step will be to go here and update your payment details.
Here you can find more information about Spotify's refund policy.
Hope this helps. If you have questions, you know where to find us.
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"Difficult roads often lead to beautiful destinations." ―Zig Ziglar