Turkish Airlines Ticket Postponement Issue

I had a ticket for a trip on August 31st from Helsinki to Istanbul, and from Istanbul to Mardin. My return ticket was for September 15th from Mardin to Istanbul, and from Istanbul to Helsinki. I purchased the ticket for a total of 597.20€. I wanted to postpone my ticket because my workplace did not grant me leave. So, I called Turkish Airlines to ask if I could postpone the ticket. The employee suggested that I make the ticket open, allowing me to use it within a year. I agreed. They informed me that I would need to pay a fee for making the ticket open. For the outbound trip, it would be 199€, and for the return trip, it would be 99€, totaling 298€. However, the amount I paid to make the ticket open was 314.71€, which means they charged me an extra 16.71€. We made the ticket open on Monday, 07.08.2023. Less than a day later, I called again on 08.08.2023 to use the ticket. The employee told me that I would need to pay 550€ for a new ticket for February 17th next year. In total, with the amount I paid to make the ticket open, it would cost 911.91€ to get a new ticket. I asked why they didn't inform me that it would cost this much when I called the previous day. The employee mentioned that there could be a fare difference. I said if they had told me it would cost this much, I would have accepted it, but now, less than a day later, I am told I need to pay 550€. I then asked if they could find a cheaper option. The employee said the cheapest option was for June 1st, costing 535€. If I were to buy a new ticket myself, it wouldn't cost more than 500€. All our phone conversations are 100% recorded, and the employee even offered me a discount and contacted me via their personal WhatsApp. The discount amounted to 80€. The account for the ticket I purchased is listed under Turkish Airlines, but the account for the open ticket is marked as unknown. I then asked if the ticket could be refunded, and the employee said the refund would only be 35€. I hope Turkish Airlines contacts me and resolves this issue, and that my 911.91€ does not go to waste. Customer satisfaction should be a priority for every company, and such situations should be resolved with proper communication and clear explanations. I eagerly await your prompt response and a resolution to this matter. (I have the number for the open ticket and can provide it when you contact me.) I hope Turkish Airlines resolves this issue.