AJet Charged Me More Than a New Ticket for a Date Change

I purchased a ticket for my son on the 26.06.2025 AJet flight departing from Sabiha Gökçen at 01:00 and arriving at Çukurova Airport at 02:35. Due to a change in his school schedule, we wanted to change the ticket. Although we offered to pay the fare difference, we were asked to pay more than the cost of a new ticket. They claimed it was a promotional ticket, but if we are willing to pay the price difference, that should be sufficient. Instead, we were directed to purchase a new ticket as part of what seems like a sales strategy, effectively invalidating our previous payment. I am requesting that my child’s grievance be resolved.