Turkish Airlines Canceled My Existing Ticket and Put It Back on Sale!

I purchased a connecting flight ticket from THY for Izmir - Tromso, with the Oslo - Tromso leg operated by SAS. However, according to a message from THY, my ticket was canceled without my consent. When I inquired about the reason, I was told it was due to operational reasons. Yet, the flight is still listed on the THY website, just marked as full. Additionally, when I called, I was told the flight was canceled by SAS. However, when I contacted SAS (Scandinavian Airlines), they informed me that the flight was not canceled and that more than half of the plane was empty. Upon calling THY again, they offered me the same canceled flight as an optional flight. When I pointed out that this was my canceled flight, the customer representative said they couldn't process this ticket. It's clear that there is a blatant lie involved, and they either oversold the ticket or are holding it to sell at a higher price. Due to THY's behavior, my plans are completely disrupted. I urgently request this issue to be resolved.