S8 microphone/noise reduction

[andyjb]

How can I turn off the poor noise reduction on the s8. Nobody can hear me properly when talking to them unless I cover the noise cancelling mic on top of the phone with a few layers of electrical tape. My voice sounds intermittently muffled and distant. Samsung have already had the phone for repair and said that there is nothing wrong with it. They have even replaced the microphone but the problem still exists.