Turkish Airlines Seat Selection and Check-in Discrepancy Problem

I purchased two Turkish Airlines tickets for flight TK1939 from Istanbul to Brussels on December 12, 2025, via the official website www.turkishairlines.com. The booking is under the name Selin Mavi with the reservation code UFCABV. During the purchase, I paid extra to select specific seats, 13J and 13K, for two passengers. When I logged into the mobile app to check in the day before the flight, I noticed that my selected seats and almost all other seats appeared to be already booked. The aircraft layout showed 8 seats per row (AB, CDEF, JK). Columns B, C, D, F, and J were full, while columns A and K looked empty, which did not seem realistic. At that stage, I could only select one double seat at the very back of the plane, in row 40, even though I had previously paid for 13J and 13K. I contacted Turkish Airlines customer service twice before the flight to resolve this problem, but when I arrived at the airport, my originally paid seats 13J and 13K were still not assigned to me. After some effort at the airport, I was finally given seats 12J and 12K instead. On board, I asked the passengers sitting in 13J and 13K whether they had experienced any issues with their tickets. They told me they had not had any problems, and that they had come to the airport without prior check-in and were given those seats when they checked in their luggage. Today, I submitted a complaint through Turkish Airlines’ own application, but I found that the complaint section there was inadequate and did not move the process forward in a meaningful way. I therefore feel that the seat selection fees I paid were not properly honored and that the seat allocation system did not work transparently or fairly in my case. I request a full refund of all seat selection fees I paid for this reservation, and appropriate compensation for the inconvenience and loss of the specific seats I had chosen. In addition, I expect Turkish Airlines to investigate this seat allocation issue in detail, provide a clear written explanation of what happened with seats 13J and 13K, and take the necessary steps to ensure that other passengers do not experience similar problems in the future.