Turkish Airlines Flexible Ticket Cancellation Issue

I purchased a flexible ticket from Turkish Airlines, but they are treating the return leg as a promotional ticket because the outbound leg was on promotion. However, when I try to change the ticket, they allow me to do so for free as if it is a flexible ticket. This is a clear violation of consumer rights, and I feel aggrieved by Turkish Airlines. I paid almost twice the normal price for this flexible ticket and I am requesting a refund for the cancellation of my ticket as per the service terms. Due to this issue, I am stranded abroad and unable to plan my return. Under these circumstances, I request the cancellation and refund of my return ticket for the Chicago-Istanbul flight, reference number UIA3PR, ticket number 2352208304668.