Turkish Airlines Flight Cancellation Issue with Extra Charges

Today, the flight ticket I purchased in Siirt for ₺1705 was canceled an hour before departure due to weather conditions. I was also informed that the flight from Batman would not take place due to weather conditions. Since I urgently needed to travel today, I had to switch to the Diyarbakir flight, which normally costs ₺1300. Later, when I informed the domestic flights supervisor about the situation, I was told that there was a flight from Batman and that they could assist with the ticket change. Since my only option was to change the ticket, I informed the sales office staff about the situation; however, they asked for an additional ₺640 as a change fee. My current complaint is about why I was not refunded the difference when the ticket was cheaper, or why incorrect information was given, and why immediate changes are applied like a penalty after the inconvenience. I request that my grievance be resolved.