Agoda Double-Charged the Same Sixt Reservation Five Minutes Apart

I booked a car rental through the Agoda app, powered by Booking.com infrastructure, from Sixt in Sarajevo, Bosnia and Herzegovina. Without realizing it, I ended up paying for the same reservation twice on March 5th — the first payment at 3:32 PM and the second at 3:37 PM. The rental period ran from March 5th (pickup) to March 8th (return). In total, approximately $291 was charged to my card twice.
Both payments were made with my Garanti Bank card. When I contacted my bank, they told me I needed to reach out to the company directly despite my objection to the charges. When I tried to contact customer service through both Agoda and Booking.com, I kept hitting automated responses and could never get through to an actual person. The removal of the Turkish language option made phone communication even more difficult, leaving me unable to clearly explain my situation to anyone.
The bottom line is that two payments were collected for a single reservation. I rented and used the car without any issues, yet the duplicate, erroneous payment has still not been refunded, and I cannot find anyone willing to take responsibility. I am demanding that the duplicate payment be immediately returned to my card and that I receive a clear, written explanation of how this happened and how it will be resolved.