Hi @Quentinlc, let me see if I can help out here!
The Xperia XZ2 Compact has two different microphones, one located at the bottom of the frame and one located at the top of the frame, to find out the exact location of the microphones, see point 2 and 11 in this overview. The first thing that i would advise is to make sure that the main microphone which is the one used for regular calls calls is not blocked by a case or any kind of dirt or grime.
Also, have you been able to carry out a quick test of the speakers in order to see if the hardware is working as intended? In order to do this, find and tap Settings > Support > Xperia Tests > Microphone and speakers.
Another thing that you can try is to reboot your phone in safe mode in order to see if the secondary microphone works better there. All apps downloaded from Play Store is temporarily deactivated while in safe mode and by doing this, you can see if this behaviour is caused by a downloaded app. For more information on safe mode and how to use it, click here.
If the behaviour persists in safe mode, I suggest that you try to repair the software on the phone using a computer and Xperia Companion. Keep in mind that a software repair will erase all user data from the phone, so it is advised to do a backup of your user data before proceeding with the repair.
If none of these measures manages to improve the functionality of the microphone, I suggest that you get in contact with your local support team to have the phone sent to an authorized service center. If you have any questions regarding the service such as routines, warranty and consumer laws, these kind of questions are best answered by your local support team as well.
Let me know how it goes!
