help with 8390 headset

[Guest lai]

i bought this headphone adapter that convert 3.5mm to 2.5mm so i can use normal stereo headphones to listen to music on my 8390. it works fine for couple of weeks. but because my stereo headphone don't have a mic so whenever someone is calling me, i have to take off the headphone to listen. then my phone is not working properly.

i start making phone calls and cannot hear what the other said through the earpiece. other people can hear me though. i have to turn on speakerphone in order to make conversation.

if this is a known problem, pls show me how to fix it. thank you.