Turkcell Billed Me Despite Ongoing Voice Call Issues

I recently switched my line to Turkcell, expecting improved service, but I quickly encountered problems with voice quality. The sound quality was so poor that I struggled to have a proper conversation, which was both surprising and disappointing, especially given Turkcell's reputation. I reached out to customer service multiple times, detailing the same problem on each occasion. Even with all the hard work put in, there was no change. It was incredibly frustrating that they still sent a bill, despite the service not working correctly from the start. I let them know I was transferring my number to a different provider because the issue was still unresolved, but they charged me regardless. This entire experience is completely unacceptable and unjust.