Turkcell Price Discrepancy - Existing Customer Forced to Pay More Than New Users

I am a Turkcell postpaid line user. At a Turkcell store in Samandıra, Sancaktepe, Istanbul, I noticed that they were offering the same tariff I use to new customers for ₺420, while as an existing customer I am forced to pay ₺540 for the same plan. I realized this situation about 10 days ago. My tariff contract will continue for 12 months. I have not yet discussed this issue with customer service. I request that the same price be applied to existing customers as to new ones, and that the price difference be corrected. My related number is 0507*****16.