PSA: The Microphone Is On The Earbuds, Not The Phone
It seems obvious, but there seems to be some confusion: if you have earbuds or headphones plugged into your phone that have a microphone built-in, then you don’t need to hold the phone up to your face.
The other person can not hear you better if you do that. Think about it like this: when you have earbuds with a microphone plugged in, the microphone has been moved from the phone, next to your face.
Also, fyi, you probably don’t need to hold the microphone close to your mouth either, but at least that makes more sense.