Turkish Airlines Baku Flight Seat Change Issue

I was given the option to check in online for a specific period. Following your suggestion, I chose my seat; however, just a minute before boarding, I found out that my seat was changed, and I was told I would be seated in the middle instead of the aisle. A different seat number was assigned! This situation is extremely frustrating and a very poor practice in terms of customer satisfaction. It is unacceptable that my pre-selected seat was taken away because another passenger paid for it. This practice should be stopped immediately; you should not be a company that prioritizes money. Prestige sometimes matters, but it seems like it is not valued here. Additionally, the new seat was at the back of the plane, 22D. I frequently fly with Turkish Airlines to many destinations. I have Elite membership and will soon become Elite Plus; however, this is the treatment I receive. Thank you, Turkish Airlines... The current state of your company is truly disappointing.