I plug in the earphones and i cant get half of the...

Question

its a black mp4 touch screen
has outside speekers and they work fine but if i plug in my earphones i have problems with every earphone i try but my outsid speeker & plug in speaker works fine. what can i do!!!!!!!!!!!!!!!!!!!!

ps it has a warinty but im not sure ware to send it to get it fixed for free