Try using hand free bro, if got audio, means ur speaker kantoi? n if no audio also, u might in a place where d connectivity is not smooth o, ur phone is really kantoi....
neway, try using hand free, play some music n video. if all no avail, go bac 1-1

call from Phone the following codes:
*#0*#

you should be able to find basic hardware test there, should at least be able to verify if you have a defective set.
might also want to switch to "Speaker" mode during the call instead of listening through earpiece, to tell if the earpiece is defective.

There is another test called "Receiver (White)" Your screen will show white color and buzzing / continuous tone sound from the ear piece. Check this out first.