Pegasus Airlines Charged Me Extra When I Tried to Change My Flight Date

I purchased a flight ticket through the Obilet app with Pegasus Airlines for April 13, 2025. I wanted to change the date to April 14, 2025, so I opened the ticket and converted my ₺1,000 ticket into a voucher. However, rescheduling it for just one day later ended up costing me ₺850. They only gave me a ₺158 voucher in return, and the rest of my money—₺850—is gone. I want Pegasus Airlines to refund that amount. Following this incident, I had to buy a new ticket for the Pegasus flight from Istanbul to Gaziantep, departing on April 14 and returning on April 19, 2025. Pegasus should fix this situation because I lost the value of an entire ticket. The PNR of the ticket I had an issue with is E8HW5N.