In recent time , we have found an issue in iPhone 7 / 7 Plus during repairs. Usually the problem occur when the phone get drop or get damage, the iPhone IC component for the audio and voice managements get detached from the circuit board and stop working. the iPhone system is an intelligent system during the itunes restoration the itune system check and test all the major component and any of them found faulty or detached then it stopped working. In iPhone 7 usually when the audio IC component get detached from the circuit board it stopped the audio function during the call time.
this problem is fixable but it is time consuming and also not cost effective. it is an engineer level job which can be carried out by our qualified staff and can fix it.
The main audio ic chip as seen in the picture is the component responsible for the audio management and cause the apple logo screen if it is faulty