Unable to hear &be heard

[lalalawani]

I'm unable to hear callers as they are unable to hear me even as call goes through.

 

[ironass]

I'm unable to hear callers as they are unable to hear me even as call goes through.

There can be any number of reasons for the issue you are facing, such as but not exclusively...

Bluetooth remaining switched on or paired to a device

Apps such as OK Google, Facebook Messenger, etc:

Headphone jack has become faulty and thinks headphones are attached.

Have a look at the following thread over on Android Central for other possible reasons and solutions...

Why can't I hear the people I call on my Galaxy S4?