Double-Charged for Cross-Border Fee by Budget at Krakow Airport

I rented a car through the Turkish Airlines app from Budget at Krakow Airport for one week. Since I was traveling to multiple countries, I paid the optional "Cross-Border Fee" through the app. However, when I arrived at the Budget office in Krakow, they claimed this fee wasn't reflected in their system, even after I showed them my reservation. As a result, I was charged the fee again. I contacted Budget Turkey 13 days ago regarding this issue, but I have yet to receive a refund. I’m frustrated by the delay and expect an immediate resolution to this overcharge.