phone's microphone is not working

Hi,

Is the phone in a protective case?

If so remove it from the case and check if you can be heard OK when on a call.

If still no good, try using the earphones with the microphone attachment or the phone in loudspeaker mode when on a call to see if you can be heard OK. This is just to prove that the voice transmission circuitry is OK.

Try using a vacuum cleaner to remove any blockage in the voice inlet hole (next to the headphone jack) that may be stopping the microphone from picking up the voice when on a call. Do not use a metal pin or probe to try and clear the voice inlet hole as the microphone is directly behind it and may be damaged.

If still no good the phone will have to be opened and the microphone's flex cable connection checked if it is secure and if so the microphone may have to be replaced. Here's a video that shows what to do.

Replacements are available online. Just search for Galaxy J6 microphone + headphone jack flex to find suppliers that suit you best.