THY Flight Ticket Issue, They Said No Seat Available

I bought a plane ticket from THY a week in advance. I tried to do an online check-in, but I was told there were no available seats. It's really hard to understand. There was no suitable seat for me on the plane I paid for. It turns out that the airline sells more tickets than the number of seats under the name of overbooking to make money. They sell non-existent seats to people for money. When this strategy backfires, they shamelessly direct people to the exit seat without any guilt. Just to make a little extra money, they gave me an exit seat. I didn't pay any less than any other passenger there. I have as much right as they do. I absolutely do not find this situation acceptable. Please do not call the act of making money by putting people in a difficult situation overbooking. Everyone knows how to make money this way in this world. Only some do not resort to this way because of their humanity.