Mic doesn't work during calls! I have Honor 3C.

My phone records sounds, in sound recorder app or capturing video with camera.
But when I call someone (or someone calls me) mic doesn't work unless I enable speaker. When it's on speaker, the mic works!!!

What should I do?
My first guess is that your phone has two mics - one for "computer-like" use, one for when you're holding it to your face - and the second of these is broken (i.e. a hardware problem). If that's right, then you should get it repaired, either by taking it back to the shop, or by finding a repair centre near you.