Turkish Airlines Refused Full Refund for My Miami Return Flight

When I requested a cancellation of my Miami-Istanbul return ticket, which I had purchased with a significant difference and a full refund, due to a change of plans, they told me they could refund half the price. I explained my situation clearly and expected a fair resolution in line with the original terms. Instead, I was met with indifference and a vague refund policy. Despite numerous attempts to contact me, write to me, and provide feedback, I haven't heard back. It's unfair and against business ethics to charge a difference and then offer half the price. My flight is just around the corner, and I'm considering taking this matter to court.