I'm hearing an echo during phone calls?

Hi!

I bought my new Samsung Galaxy A7 2 months ago

I am hear echo of my voice as I speak,

I looked on some forums and some users blame the phone case for the echo. I took the case off and the echo didn't go away. Other users have tried sending their phone in for repairs and/or complete a factory reset with no luck. Is there anything else I can try?

Thanks!