S9+

[Sumaddy]

Any one else having issue with S9+ the other part cant hear you when you recieve calls. But if you switch to speaker phone they can hear you, during that same call you can switch off speaker phone and they can still hear you then. 

[DrewHaz]

I am having exactly that problem with my S9. It works fine with headset attached, but that isn't always convenient. The other thing to note is the calling party hears a brief hiss when the call is answered. I have run diagnostic checks on microphone and checked all relevant settings and all appears ok. Even checked "answer using volume up" and it doesn't make any difference. Phone is on latest available software build

[DrewHaz]

Found the solution on another thread in here. Thanks anorrie!...
"Go to settings from top pull down. beside settings wheel is power off button. push it and when options come up hold thumb on power off button until it says safe mode....select this. When phone powers off start it up again...it will take a minute or so and will be in safe mode. Power off again normally and when you power on again it should be fixed 🤞"

[Sumaddy]

did that aswell. this issue only started after the last update. was told to do a check on it from Samsung customer service. that work for a bit.
Test the receiver.

If you are currently on a call, the call will be ended when you test the receiver.

1. From the phone dialler, enter *#0283#.
2. Select RCV Packet Loopback ON (it may appear as either Start : RCV_1stMic or RCV_DualMic on some devices).

Say a few words as if you were on a call. If you hear your own voice, it's working correctly.

[Sumaddy]

As promised here is a link with some useful information about your device.

http://lcx.me/?XasuC