Turkish Airlines Double Booked for One-Way Instead of Round Trip

Hello, on January 25, 2024, I purchased a round-trip ticket from Turkish Airlines for three people: A**** C********, K**** G****, and Y***** from Istanbul to Elazig Airport. I completed the outbound ticket and checked in. However, when I bought the return ticket, the page booked another one-way ticket instead; meaning while I was trying to book a round-trip ticket, the page made me purchase two outbound tickets. I called customer service immediately within a minute and reported the issue, but they couldn't help. They informed me that changing the ticket would cost an exorbitant amount. I don't have enough limit on my credit card, and my family is traveling there for a funeral. This situation occurred due to the page's error. I had to cancel the ticket, resulting in a loss of ₺525 per ticket. I kindly request assistance with purchasing a new ticket or a refund; Ticket No: 2352215613364.