Turkish Airlines Ticket Change Fee Issue

Hello, on October 27, 2023, I purchased a ticket for a flight from Sabiha Gokcen Airport to Gaziantep. Although the Ecofly ticket price was ₺1200, I opted for the Primefly flight at ₺1500 due to the free change and refund without deduction stated in the explanations section. When I called customer service to change this ticket for the October 28, 2023, 12:30 Istanbul-Gaziantep flight, I was charged a ₺500 penalty. Customer service informed me that there was nothing they could do about this situation and that the information displayed on their screen was as such. I do not accept this penalty. The process is very erroneous compared to the statements written, and I kindly request a refund of the charged amount. I want to purchase a ticket and fly with Turkish Airlines as it deserves. Please contact me at 553 *******46 to provide the necessary information. If there is no response, I will have to apply elsewhere. Thank you for your understanding.