Turkish Airlines Gave My Paid Seat to Someone Else on the Flight

We are enjoying! the pleasure of encountering the usual Turkish Airlines crisis again. Turkish Airlines, which charges extra for seat selection, not only changed the ticket I chose, but also gave my seat to someone else, and we encountered a new crisis inside the plane. My girlfriend and I cannot benefit from this right of the ticket we bought to be able to sit next to each other. What’s the point of paying extra for a service if Turkish Airlines doesn’t respect it? We are tired of being constantly exposed to this situation on Ankara - Istanbul and Istanbul - Ankara flights. If you are using these flights, another airline company would be a much better option.