Turkish Airlines Seat Selection Issue for Istanbul-NY Flight

I purchased a ticket with reservation code UD8RXT for a flight from Istanbul to NY on September 5th and a return flight from Boston to Istanbul on September 16th on January 14th. Later, on February 27th, I selected seats and made the payments. Since we are traveling as a group of four, we chose two pairs of seats (for a more comfortable long flight) and completed our selection and payment process. There were no issues with the ticket and seat selection in the system.

However, today I noticed that the seat selection was not visible. When I called customer service a while ago, I learned that the seats I paid for 6 months ago were sold to someone else.

The representative told me that the payment was made but the 'binding' process was not completed. I do not know what 'binding' means in your terminology. However, despite completing all the steps and making the payment months ago, I am currently experiencing inconvenience due to an issue with your system. The flight is also approaching soon. I urgently request that this issue be resolved.