1. Factory reset.
2. Remove the battery for a minute, try again.
In parting my nephew has a similar failure on a phone. Nothing brought it back so it was replaced.
My S6 Edge has not seen water nor has it been dropped. If I were to call you, I would be able to hear you, but you wouldn't hear me. Unless, of course, I had you on speakerphone. I can use my text-to-talk feature and I can talk to Google. Make no sense? To me either. My microphone works, unless I'm talking on the phone. Any ideas?

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