Iphone 7 Microphone stopped working after upgrading IOS 12.3.1

Have been using iphone 7 for quite a good time. Every thing was working fine until I updated my IOS to 12.3.1 version. My microphone stopped working after I updated the IOS. I made a complete study of the problem and I now I understand that it is due to the software. Is it really a software glitch?? How should I rectify it? I am not able to speak over the phone.