Just received two new S9 speakerphone works when we talk to each other. But a whisper when others call, everything turned up to MAX! Have to put phone to ear! So angry! Then to read this has been a S8 & S9 issue. TMobile provider!
For the microphone, there are 3 apps under system apps named Phone, use these steps for each app named phone:
Settings> Apps> 3 Vertical Dots> Show System Apps> Phone> Storage> Clear Cache> Clear Data
Please let us know if these steps help any.
Phone are under warranty at Tmobile for one year. I had the same issue. You only have to pay 5.oo when you pick up the Warranty phone in store. You have to submit it through customer service