Cannot hear caller but the caller can hear me, but works on speaker

Hi everyone,

A friend's Nokia Lumia 925 phone is having a problem which I think is down to the speaker but I would like a second opinion. I am kind of the resident IT expert for most of their family.

Whenever they make or receive a call, or use Skype's voice functionality, they cannot hear the other party whilst the phone is NOT on speaker. However, as soon as they change to the loudspeaker, they can hear the other person perfectly.

Does the Nokia Lumia 925 have two separate speakers? One for normal calling and one for the loudspeaker functionality?