Apple iPhone 11 Sound Issue

Around a year ago, I bought two 64GB iPhone 11 phones from Vatan Bilgisayar, one for my daughter and one for myself. I initially missed it, but subsequently recognized there was a problem with my phone, which I took to an authorized service center when it was four months old. The issue is as follows: During WhatsApp video group chats, my voice fades to the opposite side. When someone else in the group talks and I respond, my voice cuts off and does not reach the opposite side. When the speaker ends and there is silence, my voice is heard on the other end. I also bought the same model phone for my daughter. When I place my SIM card into the other iPhone 11 64GB phone I purchased, I have no problems with WhatsApp or Face ID video calls. I found the issue was only with my phone. I explained the scenario to the service agent in detail, noting that my voice is low on WhatsApp and from the external speaker, which can be difficult to comprehend. My phone remained in service for two weeks, but they insisted there was no problem. I got my phone back, but the troubles persisted. I insisted on a thorough inquiry and stated that the problem had occurred, so I submitted it to the service again. Upon examination, they declared there was no problem. Instead of being dragged through services for the fourth time, I opted to give up my iPhone. I said, "Enough," since there was a problem. I didn't want them to replace my phone; instead, I wanted them to utilize and test it as I specified to remedy the problem, but this did not happen.