Modern phones can do a lot, but making phone calls is the most basic function.
A lot of users have been complaining about call issues on the latest Galaxy S9 and the Galaxy S9+. Users from around the world have been complaining about distorted voices, muted voices, or their phone calls simply dropping. And what is the use of a phone if it can’t make a phone call?
The issue seems to affect some users fro Europe, Middle East Africa and Australia. The build numbers are G960FXXU1ARD4 for the S9 and G965FXXU1ARD4 for the S9+, with slight region-based variations. There aren’t any security updates here or whatsoever, but “improved quality of Wallpaper” is mentioned.
Source: Android Police