Sixt Security Deposit of €300 Not Refunded After Düsseldorf Rental

Between July 15 and July 24, 2024, I rented a Nissan Primera from Düsseldorf Airport (Reservation No: 9602905571). Although I returned the car on July 24 in full and proper condition, the €300 security deposit that was blocked on my Visa World Eko card during the rental has still not been refunded. I already contacted Sixt customer service by email, but I have not received any response. This is the first time I have encountered such an issue, and it has caused unnecessary inconvenience. I request that the €300 deposit be released and refunded to my card as soon as possible to resolve my grievance.