How do I get rid of voice feedback/echo on Samsung Galaxy S6?

[klear6]

A couple months ago my mom took the leap from iPhone to android. So I got her an S6 from T mobile and ever since she has had it about 75% of the time she hears her own voice echo during calls (whether she makes them or receives them doesn't seem to matter).

I am trying to rule out what this could be from before I get it swapped out from the store. I don't want to trade it back in for another one that is going to do the same thing after I set it up. Is this a hardware problem with the mic? Is it a settings conflict? What is going on here?

I really don't want to spend hours researching how to fix it only to find out it is a hardware problem that I can't take care of anyway.

ATM she is running the latest version of lollipop but my husband got marshmallow today and he has the same phone so I am assuming she will be getting it too...

Please help me out! Thanks guys
- klear6

 

[B. Diddy]

A common cause of echo is a case that blocks the secondary mic. If your mother's phone is in a case, ask her to remove it and do some test calls.