Pegasus Can't Change Flight Tickets Because of Their System Failure

We are attempting to modify the dates of our international tickets with Pegasus, paying the fare difference. The system indicates a fee difference of ₺5000 for the desired ticket change. Despite the amount being deducted from my card, the ticket change has not been processed. Following customer service advice, we tried multiple times with credit cards from different banks, but the change process couldn't be completed. A total of ₺20,000 appears in provisional funds, debited from four different cards five times. It is unclear when this amount will be refunded to our cards. Although customer service mentioned that the change process could be done through them, they would charge an additional service fee of ₺2000. Even if we try customer service and provide the same card information, I do not know what will change when they perform this transaction. In the end, despite paying the fee for our tickets with change rights, we cannot make the changes, and Pegasus, which causes this distress, cannot explain the reason behind this problem.