I cannot hear phone call recipients unless handset is on speaker. Why might that be?

[AC Question]

Either making or taking calls I cannot hear the other person unless I put the phone onto speaker mode and then everyone hears the call. Have I mistakenly switched on something or other preventing the audio from coming through the phone ear piece.

 

[AlphaTango414]

Do you have hands free capable head phones plugged in?

Do you have a Bluetooth device that can support voice call connected to the device?

Can you hear the phone ring while making the call waiting for them to answer? If not, sounds like a bad speaker.

 

[paddybry]

Nothing plugged in and bluetooth is off. Can't hear it ringing either unless I put it onto speaker. It's a Samsung Galaxy S5 if that makes any difference. Thanks for response