Garanti Bank Did Not Apply the 6 Installment Plan for My School Payment as Promised

I enrolled in Garanti Bank's +6 installment campaign for school payments through the mobile app. After completing the school payment, I realized that the interest-free 6 installments were not applied. I contacted Garanti Bank’s customer service, and they informed me that my participation in the campaign was visible and that they had created a request. However, when I spoke to another customer service representative, they said that I had not enrolled in the campaign. The fact that everyone is providing different information is really confusing. Why should I have to pay an interest of ₺45,000 because of the bank’s negligence? I will pursue my rights regarding this issue to the fullest and share the problems I’ve experienced on every platform, as I am considering ending my relationship with Garanti Bank.