Turkcell International Data Usage Complaint

I am a Turkcell customer using the Mega Dolu 60 GB tariff, and I am writing regarding an unfair international data charge that appeared on my December bill for the line ending with 8654. On 28–29 November 2025, I was in London, United Kingdom. During this entire period, mobile data for my Turkcell line was completely turned off, and mobile data was enabled only for my Holafly eSIM. My phone is dual SIM, and while calls and SMS were active on the Turkcell line, mobile data and data roaming for Turkcell were entirely disabled. Despite this, I received SMS messages indicating that an international tariff had been activated, even at times when I was not actively using my phone. Although Turkcell data roaming was turned off and all internet access was provided exclusively through the Holafly eSIM, an additional charge of approximately 1,050 TL was reflected on my December bill with the claim that I used mobile data abroad. I did not use Turkcell mobile data in any way during this period, and I consider this charge to be completely unjust and a financial loss for me. When I contacted customer service, I was told that their system showed data usage abroad and, based on this, they refused to open any complaint or request on my behalf. This is not the first time I have experienced such a problem; in the past, I also had to file a billing dispute because I was again shown as having used mobile data abroad when I had not. Repeatedly facing the same issue and being told that “the system shows it this way” without any real investigation is unacceptable. I am being charged for a service that I absolutely did not use. I request that the international usage charges unjustly added to my December bill be canceled and fully refunded, and that a detailed technical investigation be carried out to prevent similar mağduriyet from occurring again.