Turkcell Low Internet Speed Issue

I have been experiencing mobile internet speed problems on my Turkcell postpaid line for years in Adnan Kahveci Neighborhood, Beylikdüzü, Istanbul. In speed tests performed at the same location, Turkcell reaches around 5.4 Mbps, while Vodafone reaches around 8 Mbps. Even though we have tried different phone brands and models, the result does not change. As can be seen in the speed test screenshot I uploaded, the values do not go up to a higher level. This problem continues almost constantly throughout the day, and especially when there is a power outage, the internet speed drops even more and the line becomes unusable. On days when I could work remotely, I am forced to go to the office just because I know that if there is a power cut, I will not be able to connect properly via mobile internet. I have contacted Turkcell customer service at least 10 times about this issue so far, but each time I have been told that everything is normal and no solution has been provided. Despite this, I expect customer service to act in a truly solution-oriented manner, to handle the issue seriously and, if necessary, to dispatch field teams to my home, perform a speed test there and detect the problem on site. Instead of focusing on advertising and marketing activities, I request that infrastructure investment be made especially in the Beylikdüzü Adnan Kahveci Neighborhood area and that a permanent solution be found for this chronic speed problem. As a long-time Turkcell customer, I expect a service where I can receive the value of what I pay for.