Why can't people hear me on the other end even if I am screaming?

I have been having audio issues with this P8 + Huawei phone every since I got it where the person who I am speaking to says they can barely hear me even after adjusting the sound on the phone. It's weird how on my other lower ram phone people could hear me perfectly fine, now with this phone people say the audio is muffled and like I am talking from a very very far distance when in fact the phone is close to my face and I am literally screaming. Talking with a headphone jack plugged in or while on speaker makes the issue worse. Any suggestions on what the issue could be?