Really bad echo and other people cant hear me

I replace a customers pwr flex cable and battery. She then called me and said that she was having problems hearing. After some questions and testing the only thing I saw that was a problem was other people cant hear her talk. (she said she just got off the phone with someone) I have made test calls and same problem every time. Phone plays music and I can hear on the phone through speaker and loud speaker. It will not record sound when recording a video.

I have ... Cleaned everything including little mic hole on top. I have replaced the loud speaker. I also saw a video that told me to put pressure on sound part in the logic board by putting a few layers of tape.

Now I have a major echo when I talk into the phone but still the other party cant hear me.