Denizbank-Pegasus Dispute: Invalid Installment Agreement for Flight Tickets

I made a deal with Denizbank to buy flight tickets from Pegasus. The agreement was split into three payments. So, I tried this promotional campaign for the first time and ran into a big problem. They didn't give us the benefits or discounts they promised in the campaign. I asked for help from both Pegasus and Denizbank to solve this problem, but they couldn't help me. So, I'm really disappointed and it's really getting to me that there's no support or solution for this issue. I thought they would keep their word in the agreement, but it looks like they've unfairly excluded me from the benefits they promised in the promotion. It's really frustrating, especially since I followed all the rules, but I haven't been able to get any help or support to solve the problem. It's made me feel really upset.