Hearing voice is very less

This is a common issue, assuming things liek speaker phone are working normally and the phone is behaving normally otherwise.

You can clean the earpeice grill with Methylated spirits from a hardware store and an old toothbrush.

Wet the toothbrush with the alcohol and brush the metal grill of the earpeice, this will remove dirt and grime from the metal grill, allowing sound to pass through again.