THY International Flights Non-Refundable Ticket Issue

Hello. I purchased round-trip tickets for Istanbul-Los Angeles and Los Angeles-Istanbul flights for myself, my wife, and my son. Since the departure date was fixed due to both tourism and business purposes, I bought non-refundable tickets for the departure. However, considering that my business meetings might extend, I paid a 'substantial extra fee' for 'fully refundable' return tickets. Due to my business meetings, my return date is not fixed, and it is certain that I will not be able to return on the valid ticket date. Unfortunately, I couldn't resolve my issue through the mobile app or the call center because I was informed that due to company policy, since my initial ticket is non-refundable, my return ticket is also non-refundable. However, I paid a 'substantial extra fee' for my return ticket and was not informed about this policy. If such a policy exists and the departure ticket is non-refundable, the system should also make the return ticket non-refundable. I want to use my 'fully refundable right' that I am entitled to. I requested that the full amount of my return tickets be refunded to my credit card as soon as possible, but I received an inappropriate response in the information form stating, 'We recommend that you review the rights provided by your ticket more carefully next time.' I expected better customer satisfaction from a world-renowned company like THY. I will continue to seek my rights to the fullest extent.