Issues with speakerphone during calls

Hey,

So apparently whenever I have a call on loudspeaker (WhatsApp or normal calls) the person on the other end can't hear me?

I tried doing a test by using the recorder app and that picked up my voice fine so now I'm stumped….

Does it use a different microphone when on loudspeaker? And if so where is this located so I can check if it's blocked or anything?

Tia for any help