Iphone microphone not working

Hello,

I was using my iPhone XR today, and I realized that there are some issues with it. I cannot use the phone app. It works on speaker, but it doesn't work normally.

Before anyone recommends the troubleshooting steps, I have already done them. I tested it with memos, videos from both cameras and all that. I know it's not the issue of the microphone because it works perfectly on applications such as Messenger, where there is no difference. It is only the phone app, particularly when I don't use the 'speaker' option where it just stops working, and has that static type noise. You can only hear me when I talk while basically kissing the bottom of the phone.

Is this a hardware issue I am completely unaware of, or is it some kind of software one? Any help would be much appreciated.