When i'm talking to someone on iphone, their voice is low. What is wrong?

When i'm talking to someone on iphone, their voice is low. What is wrong?

Try turning the volume up on the side when In a call or that person is talking to soft.

Have you tried turning up the volume while your actually on the phone because the call volume is separate from the phone volume.

Mine does the same thing! I'm still not sure, but try taking it off silent and turning the speaker volume up. Hope this helps?

Maybe something wrong with the phone or the person may be in a bad signal area or even you as well.