Enuygun Changed My Return Flight Without Notice – Denied Boarding by Aegean Airlines

I purchased round-trip tickets to Montenegro from Enuygun, with a return flight scheduled for June 18 at 5:35 PM with Aegean Airlines. When I arrived at the check-in counter, I was told that my name wasn’t on the flight list. I showed the staff my booking details and screenshots from Enuygun, but they were equally confused and referred me to a supervisor. The supervisor informed me that my and my spouse’s tickets had been moved to June 15 by the travel agency, and they provided a printed document as proof. When I contested this, I was met with rudeness and hostility, with the supervisor throwing the paper at me and saying there was nothing they could do, and I should contact the agency. They were dismissive and refused to help, leaving me stranded without any resolution.