THY Flight Issue with Direct Flight Turned to Connecting

I purchased a direct international flight ticket from THY, only to be informed later that my flight would be operated by Ajet and that my direct flight had turned into a connecting one. I called both companies, but they kept passing the responsibility to each other. I then visited the THY office, where they offered me two options: either a refund or a connecting flight with them. I reluctantly chose the connecting flight with THY because the other option was a connecting flight with Ajet. Now, due to my lack of confidence in taking a connecting flight and because all my plans have been disrupted, my vacation has been moved up by a week since the connecting flight is a week earlier. THY has caused me significant inconvenience. They are now offering me a refund of ₺900, which feels like a mockery. I am expressing my grievance, and while they acknowledge my situation, they are not taking any action.