Despicable behaviour by Comair controller at Cape Town International airport.

This is now the third time that I have been bumped from my pre-booked seat by the Comair controller at CT International over the past 2 months. He/She, to my mind is being allegedly, perhaps "bribed" is too strond a word, however something is definitely taking place to bump whomever has booked an exit/isle seat and I can only presume to give it to a friend/ acquaintance. The first time I did not check my ticket and found that I had been reallocated from my exit row seat to another isle seat. As I had not checked the ticket when it was issued, there was very little I could do about it. The second time, I did check the ticket and found that my exit seat had again been changed to a middle seat on another row. I informed the ticketing lady this was unacceptable and showed her the payment. She went off to the controller who basically said, "too bad so sad" take what you have been given. Or perhaps the Comair software, perish the thought, is inadvertantly selling the same seat to more than one person, however judging by the attitude of the controller I seriously doubt it. It has happened again today 26/04/22 and again the ticket was not checked so very little could be done about it. Comair this is simply totally unacceptable, what are you going to do to ameliorate this unacceptable situation?