Hi understand some folk calling a Samsung phone experience an echo, often unbeknown to the holder of the Samsung phone, unless the caller complains.
I have posted on this issue here (as have others):
I initailly thought it was an /e/OS issue, but it appears the fault lies with Samsung devices.
Many threads across the internet complain of this problem:
One must assume it is not all Samsung Phones that have this issue, but it would be good to know as a percentage how many users do suffer from it:
I have experienced the Samsung Devce Echo
Regain your privacy! Adopt /e/ the unGoogled mobile OS and online services
Never experienced this issue with my S9+, when called by at least 5 different owners of Samsung phones I can think of (but for sure more).
No experience of echo on Samsung A3(2016) a3xelte.