Turkish Airlines Complaint Regarding PrimeFly Ticket Change

I purchased a PrimeFly class ticket from Turkish Airlines for the Boston–Istanbul route. At the time of purchase, it was explicitly stated that this ticket allows free changes to the flight and that same-day changes to earlier flights are permitted. However, I was later informed that changes could only be made up to 3 months before the flight date, based on a rule that was never clearly disclosed during purchase. This hidden rule has effectively restricted my right to change the ticket. For approximately one month, I have attempted to change this ticket through the Turkish Airlines website and mobile application, but each attempt has resulted in a system error, preventing the transaction from being completed. Because the online channels did not function properly, I was directed to the call center, where I was asked to pay an additional 15 USD for the change. Since the problem arises entirely from system issues and from the application of a rule that was not disclosed at the time of sale, I do not accept being charged this additional fee. My PNR code is URRVKS. In addition, due to my sister’s serious health condition, it is realistically impossible for me to take this trip as originally planned. Despite this, her condition was ignored, and because of both the system errors and the later-imposed hidden rule, I was prevented from exercising the change right that was promised to me under the PrimeFly class. In my view, these circumstances clearly constitute misleading sales and defective service. I request that my free change right under the PrimeFly class be honored and that my Boston–Istanbul ticket be changed free of charge to a later date, no later than March 23. If this is not possible, I request a full refund of the ticket price.