Chosen Solution
I have an iphone 6s which works pretty well. Recently I have had a problem with receiver/speaker - it seems to work well when I call some people .. but for my friend for example I can barely hear him, even when I plug my headphones on. His phone is working perfectly fine and he has no problems hearing me. What could I do to fix it? I’ve tried everything.
That’s odd. Is your friend on a specific carrier which is different to those of the people who can call you just fine? If so, it would be a problem with the board receiving calls from a certain carrier.