Turkish Airlines Overcharged Me

One week before my THY HOUSTON-ISTANBUL flight, I contacted a THY customer representative on October 16, 2023, at 21:50 (US time) to book my baby's ticket. The representative informed me that the ticket would cost around ₺1,300 but that the payment could only be made at the airport. I mentioned that my friends had been able to pay a similar amount through the app, and I questioned why I had to pay at the airport. However, I did not receive a satisfactory answer. When I asked if the amount was definitely around ₺1,300, I was assured it was. Upon arriving at the airport, I was charged nearly three times that amount, specifically $125. They did not accept cash, and I did not have a credit card with me, so I had to plead with strangers to make the payment. I am requesting an explanation from THY for this incident and a refund of the amount I paid.