iPhone 7 microphone not responding

Here are the suggestions I found in Apple Support:

If the microphones on your iPhone aren't working - Apple Support

Clear the microphones

1. Remove any screen protectors, films, or cases from your iPhone.
2. Clear any debris from the openings of your iPhone. 

Contact Apple Support

If you still sound unclear during calls, recordings, or apps, contact Apple Support to discuss service options.

Roshan1333 wrote: "Yes! It’s original battery

never changed, 73 % only"

73% is not healthy and is to be expected for an original iPhone 7 Plus battery. Apple considers 80% to be the level at which a battery should be replaced. So have the battery replaced and then the microphone will probably work:

iPhone Battery & Power Repair

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

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Roshan ~ Does your iPhone 7 Plus still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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