I have redeemed a voucher and money was still debited from my account? Why?

For security reasons, some providers initially debit your payment method despite the voucher, but ultimately do not debit anything. This means that you will initially see a reserved amount in your banking app for a few days (usually €3 - €10). However, if you check again a few days later, nothing has been debited. To be on the safe side, check the provider's invoice.