Turkish Airlines Ticket Cancellation Refund Issue Despite Eligibility

I had two round-trip tickets from Adana to Ankara with the reservation code UMM8YK. My first ticket had a cancellation and refund eligibility for approximately 500₺. (This is shown in the online ticket I received, and I have attached a photo as proof.) I decided to cancel my first outbound ticket and checked the rights. I called customer service and spoke with Ms. E---. She told me over the phone that she couldn't process the cancellation/refund for a single ticket and advised me to do it through the app if possible.

I logged into the app and clicked on ticket cancellation from the ticket management section, as shown in the attached photo. -Not change.- A penalty of approximately 500₺ appeared, which I paid, and I canceled the ticket. However, I did not receive any email regarding the refund of the ticket price. I called customer service again and spoke with Ms. F***. She told me that I had converted the two tickets into a single return ticket and that no refund would be issued. Why would someone convert two tickets into one for approximately 500₺?

Additionally, I clicked on the cancellation section, not the change section. I am sure that my ticket had cancellation rights. Now, not only have I not received a refund for my 2510₺ ticket, but I also paid a penalty of approximately 500₺. There is no ticket, and I am out 3000₺. And this happened just by clicking on cancellation. I request that my grievance be addressed. There is an inconsistency either in the email, customer service, or the app. All three are under THY's responsibility.