My Samsung S4 phone had a few problems for more than a year
1) Echo - The hearer would hear his own voice echoed back at him when he speaks to me.
2) No loud speaker - The loud speaker did not work. If I switch it ON, the call got cut.
3) The mute button stopped working too.
I went to the Samsung store a year ago and they said that they have to change the display and that would cost me Rs 7000 for that.
"RS 7000 FOR THE DISPLAY ?", I screamed inside and said "No thanks", took the phone back with me.
I was using the phone with all the three handicaps for the last one year.
Last week, when I was getting out of bed, the phone fell down. I reassembled the phone and now I find that all the 3 problems are solved.
AND THEY ASKED RS 7000 FOR THAT
If you have any problem with your phone, just drop it down and re assemble them. It works. If it does not work, buy a new phone.