Issue with Turkish Airlines Ticket Change and Refund Policy

I purchased a round-trip ticket from THY for my spouse. THY canceled the outbound flight, forcing me to make a schedule change. When I wanted to change the return ticket, I was told that I only had one change right and couldn't make a second change. However, I didn't change the outbound flight voluntarily; THY canceled it. Therefore, my right to change should still be valid. They have taken away my right. In complaint records 10151972 and 10192489, they continue to claim they made no mistake. Moreover, THY demanded ₺1,741.06 for the return change but said they would deduct ₺400.00 if we canceled the ticket. Since canceling the ticket with a ₺400.00 deduction and buying a new ticket was cheaper than paying ₺1,741.06 for the change, we had to cancel due to their imposition. I don't understand this business logic. Additionally, they should have deducted ₺400.00, but they deducted ₺716.00. I am seeking my rights. I want my grievance to be resolved. I expect them to accept their unreasonable practice. I am complaining. Attached is the SMS from THY confirming the flight cancellation. It is unacceptable to claim that I made this change voluntarily. Therefore, I am aggrieved.