Had a strange one earlier, I was on the phone to my brother and volume was a bit low, tried the volume key with no success.
I then moved the phone away from my ear and tried again and the volume went up.
It seems the volume key is disabled when the phone is against my ear, possibly a glitch with the block accidental touches thing.
Mine had the same issue of very low incall volume and I just cleaned it with an old toothbrush and I just cant believe how the volume opened up.
I spent hours googling my low volume during calls. After trying resets, and following different directions on this and that, and looking at YouTube videos. I can across this website with the answer to my problem. 1 minute later. That's the time it took me to get an old toothbrush and clean my ear speaker. I was back in business. I had to turn down the volume because it hurt my ear the volume was so loud. Thanks so much!
It worked for me too, planned to get my earpiece replaced and i came across this feed and it just miraculously worked it out... its now like as it was out of the box when purchased