I have an iPhone 5s. My microphone doesn't work when the speaker function is on. What is wrong?

It appears that you've come from this article: If the microphones on your iPhone aren't working - Apple Support. I'm assuming that didn't help you?

Try restarting your iPhone first, and if that doesn't fix the issue you're experiencing, I suggest contacting Apple Support.

-- Jay (they/them)

Did you read the article at the top left of this thread & follow the steps?

If the microphone still doesn't work, contact Apple Support -> see Related Article.