Turkcell Gave Me 3 Mbps Instead of Promised 150 Mbps - Refused Free Support

On April 8th at 21:41, I spoke with a customer service sales representative regarding a Superbox application. During the call, I was informed that I would receive an internet speed of approximately 150-200 Mbps, which is about half of the advertised maximum speed. However, it has now been 6 days, and the speed I receive is consistently between 3-5 Mbps, occasionally reaching up to 10 Mbps, and rarely up to 20 Mbps. None of the promises made during the sales call have been fulfilled. When I contacted customer service again (on April 20th, Sunday at 20:38), I was told that I would need to pay ₺600 for a technician to come and resolve the issue. This is unacceptable. Given the commitments made during the initial conversation, I am formally requesting either a cancellation of the service without any commitment or penalty, or the dispatch of a technician at no additional cost. If this request is not fulfilled, I will escalate my grievance through every necessary legal channel available.