Türk Telekom Charged Me an Unfair Termination Fee After Misleading Information

I was a Türk Telekom postpaid line user. I decided to switch to another operator and, when I inquired about the termination fee, I was informed it would be ₺840. I switched to a different operator, but two months later, I received another bill from Türk Telekom for ₺1,653.79, even though I had already paid my final bill. Customer service claimed this amount was the termination fee. Being informed that the termination fee was ₺840 and then being charged ₺1,653.79 constitutes unfair gain. I was considering switching back to Türk Telekom and was looking at their plans, but after receiving this bill, I no longer want to. I request the cancellation of the excessive charge and the issuance of the correct bill. If the necessary assistance is provided, I may consider returning to Türk Telekom.