Turkish Airlines Refusal Of Refund

I booked a flight with Turkish Airlines but realized I had booked the wrong date, so I paid to amend the booking. Turkish Airlines then changed my revised flight, which I had to cancel as it was inconvenient. They refunded me the flight cost but refused to refund the cost of changing to the flight I then had to cancel because they amended the flight. It doesn't seem right to me. I've completed three feedback forms, made one phone call, and emailed two senior officials (from whom I am still awaiting an acknowledgment).