İş Bankası Made an Unfair Deduction When I Bought Foreign Currency and Gold

I bought foreign currency from İş Bankası with 1,620,000, but after deductions on gold and dollars, 120,000 ₺ was cut, leaving me with a total of 1,500,000. The deduction was significantly higher than the market rate, and I deeply regret my decision. I was not informed about such high deductions in advance, which makes this situation even more frustrating. When I checked exchange rates at other banks and financial institutions, I realized that the cut İş Bank applied was much larger than usual. Since I purchased foreign currency and gold through İş Bank, I did not expect such a large difference. I have always trusted İş Bank for financial transactions, but this experience has made me question that trust. After all, I am your customer, and I expect fair and transparent transactions.