Echo feedback problems

[karol]

hi everyone I'm karol. and new to this forum. I have the Samsung galaxy s4 mini. I have had echo problems for well over a yr. I'm on contract with virgin. and during all calls I hear myself talking back. my voice echoes back to me. sometimes I'm unable to hear caller because of it. my phone has been sent back away twice to virgins tech team comes back with same fault plus new ones like keyboard now sluggish. any advice pls.