THY Ticket Cancellation Charge Issue

On June 13, 2024, I had a round-trip ticket from Istanbul to Seattle with THY, with the return date on June 25, 2024. According to the ticket terms, I was eligible for a refund of around ₺3,000 from the ₺34,000 I paid for the ticket upon cancellation. The call center representatives informed me that I could cancel the ticket via the mobile app to avoid extra service charges. I individually canceled my departure and return tickets via the mobile app. For the departure ticket cancellation, the app charged me approximately ₺27,000, and for the return ticket cancellation, I received a refund of about ₺1,000. Instead of receiving a total refund of around ₺3,000, I incurred an additional loss of approximately ₺26,000 due to incorrect guidance. When I contacted THY about this issue, they claimed that I made a deliberate change rather than a cancellation and that there was no technical error, thus holding me responsible. I am dissatisfied with THY's behavior, as they charged me an extra ₺26,000 for what they deemed a change, despite it being a cancellation of two consecutive tickets.