My headphone has a built-in mic and has only 1 jack, either the mic doesn't work or i can't hear sound. please help!

[Swaggy Troll]

i have a Denver BTH-203, i use the jack for the computer and without jack for phone. on PC i cant find a way to use both mic and hear sound/music. i am not sure if it's called jack or cord on the microphone but i think someone will understand.

 

[alexoiu]

Does the jack look like

(4 pin).
or

(3 pin) ?