Apple iPhone 13 128 GB Brightness Issues and Sound Problems

Hello. On June 23, 2023, I purchased an iPhone 13 128 GB from the Gurgencler store. After a few days, I noticed fluctuations in the screen brightness, as if a faulty light was flickering. It's like an electrical surge happening on the screen, and then it stops after a few seconds. I took it to the technical service center for repair. They returned the phone to me after 3 days, claiming no issues were detected, and they only performed a software reset. However, this morning, when I started playing music, I realized the sound was very low. Additionally, when the music starts, the screen brightness behaves oddly at the highest volume setting. As you can understand, the phone I sent in for repair has returned in an even worse state. I am extremely frustrated by this situation. I demand a replacement with a new device. It is unacceptable to cause such inconvenience to customers, especially considering the high prices paid for the product.