I face the same issue. Callers can't hear me but if I call back then they can hear me fine. Started happening after OTA update.
Thanks for the speaker trick workaround. Samsung had completely screwed up this update.
Thanks so much for this work around. It works for me but annoyed that I've tried everything listed except the factory reset and nothing has changed. I don't want to do the factory reset as it's time consuming getting everything back on the phone. Come on Samsung. Fix this problem!
I have the same problem and I know some colleagues with S9 who also have the same issue. And they started after an update back in November, and persisted through at least 2 more updates.
I am also seeing that when I am talking to someone and I get a new call, both calls end up hanging up. Which is rather annoying as well. Am I the only one with this second problem?