Turkish Airlines Changed My Seat and Ignored My Paid Extras

Although I made extra seat selections on the flight I purchased from Turkish Airlines, the company changed the aircraft on the last day to accommodate more passengers and completely disregarded the extras that we, as passengers, had paid for and were supposed to benefit from—without offering any refund. I specifically chose my seat for comfort due to a medical condition, and the change caused me serious discomfort during the flight. No one even informed us in advance about the aircraft change or the removal of our selected extras. I will not buy any tickets from this company again, and I want my payment back.