Unable to hear anyone on any incoming calls, can only talk if using the speaker?? Just got the phone from a used dealer?

Check the microphone. Record your voice with the built in app. If it's recording just fine is most likely a software issue.

hi :) i u cant hear people talking,that not mike problem. mike problem is people cant hear u talking. i think your speaker was spoil already,that why u cant hear the voice incoming or ringing.u better send for check again :)
if my solution useful,please voted me.thanks..

network problem connect to manually

you can check if you speaker is broken by using a set of headphones. if you don't hear sound when using your headphones there is something wrong with your software settings. if you do hear sounds using your headphones you need to replace your speaker. You can buy a replacement speaker on ebay and do this yourself, of search for someone to do if for you. If you still have warranty on your phone just return it to the shop that sold the phone.

phone ring low. how do i turn up the volume?

your speakerphone may have been damaged

Seems your ear speaker has a problem. It need to be changed.

okkk master reset ur phone if it dont works flesh a newer software