Speakerphone low volume on Samsung Galaxy S9 (software bug)

I have been using a Samsung S9 for the past three years. Recently there is a software bug that is causing a strange problem. The volume of the microphone at the top of the screen is really low for calls and audio messages. The speaker is still in perfect working condition. I tried testing the microphone by dialing the Samsung hardware test code *#0*#. For the test, the speaker is really loud and is in perfect working condition. However, when we try to use the speaker for calls and audio messages, the volume is really low. What is the reason for this? Is this planned obsolescence? Is there any way to fix this? I plan to root the phone, use Busybox, and then increase the volume level of the microphone. Can anyone please help me with this?