Bad Call quality remains after last update WW-16.1220.1906.167
I have the same issue with last firmware, bad bad call quality sound.
I think is poor now than the previous firmware, i have to use a external earphone to talk with the person or constantly, "hum, hum hum, what do you say?!?!?"
I think is time to ASUS call all phones to factory and replace the call speaker of all phones, this is not a software problem, this is a hardware problem and the only way to solve is change.
I don´t believe with software they can solve the quality sound because de hardware (speaker) can´t do better.