Is it possible the call connection to the Samsung Agent was lost and not as you say cut. Most agents are still working from home due to these unprecedented time's.
As a process of elimination try your sim card in another phone and then see what happens.
Other contributory factors could be the network masts , weather or sim card glitching.
I wish you all the best with this.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
If by doing a call test with the same sim in another phone the problem is not present what you are telling makes me think about a mic issue.
Press on the dialer *#0*# and perform the mic test and share your results.
Also you may want to use the recorder app to test both mics.