Which microphone is used during FaceTime video call in iPhone SE? I have an issue with my iPhone SE running iOS 11.4.1. I already spoke with support, and they are saying that it is hardware issue.

Do you know which microphone it is used during video conversation in FaceTime? Because this microphone works pretty well, but when I record something in Camera app, I hear only noise. Whatsapp, Messenger, Siri can't hear me too.

I already did a fresh install of iOS using iTunes. If this is hardware issue, then microphone shouldn't also work during videocall on FaceTime, or FaceTime is using other (bottom) microphone. Can someone confirm?
After doing much research as I have similar problem on my daughters phone, it seems apps like WhatsApp when on speakerphone use the front top microphone where as FaceTime on speakerphone uses front bottom microphone. Easy check is to record a front face video and hear of sound is captured.