Corendon Airlines Ticker Alteration Resulted In Crazy Fees

We purchased a ticket from Corendon Airlines for Antalya to Amsterdam through Enuygun.com. My friend mistakenly marked the wrong date, and we noticed it right away, so we started calling the airlines. Other airlines allow you to upgrade the economy ticket and change the flight. However, Enuygun claimed they couldn't do anything and that refunds, cancellations, and changes were Corendon's responsibility. I contacted Corendon multiple times. Despite explaining it was an honest mistake, they demanded an extra ₺9,000 to change the ₺8,800 ticket to the ₺6,600 one. We ended up buying a new ticket for ₺6,600, and the ₺8,800 went to waste. When I mentioned the lack of ethics and customer satisfaction, the gentleman at the Corendon call center insisted that we chose this option ourselves. They argued that changes and refunds weren't possible for economy tickets, as stated on their website. When I threatened to file a complaint, they casually replied that I could complain wherever I wanted.