It is just shifted to your control center, earlier samsung used to show it at both places but as customer said about the accidental touch they completely removed it from call screen and kept it as it is in the control center
As per your query, we want to inform you that this feature focuses on the sound, while you are on call with someone. When you are on a call with someone, a Mic icon will come with the calling number, you need to click that number, and your voice focus mode will be on.
If the issue persists, kindly report the problems with a log file. To share a log file, click on the Samsung Members Application (Open Samsung Members Application > Support> Tap on send feedback> Choose Composer> Select error report> select the appropriate issue category> Type your query and send).
