Echo on recipient side on S21 only in speakerphone mode

[dmo]

I have a brand new Galaxy S21 and when I am speaking to someone on the phone, if the phone is in speakerphone mode, the person I am calling hears an echo of themselves. I do have a phone case (Speigen liquid crystal case) that is on the phone. Is the case the reason? 

Any help is appreciated, I do like to use speaker mode quite a bit.

[xSteveuk]

Hi,
Try below
Go Settings - Apps
Look for Bixby Service
Storage
And just clear the cache

Bixby uses the mic also
And see if that helps
Resolves the echo

Also When on samsung members page
Run a diagnostic test
Clicking on the get help button
Mic test

Failing that perhaps a reset
(((Backup phone if do reset)))

[GoanGeek]

Obviously they will hear themselves as they can hear it from your speaker phone .

Better to you use a Bluetooth head set or without speakerphone.

It would be same if they put you on their speaker you will hear yourself as well.