HI all. wondering if you guys can help me out.

i have a treo 600 from China, but i'm in canada using Rogers service and works. but my headphone that came with the phone does not work. i went to RadioShack and tested their entire cellphone headphones and none worked. Except one. This headphone has following:
- 3 black rubber things at the head of the jack(so separated to 4 silver parts)
(regular onces with 2 black rubber things.)
- listing talking is fine
- has push to answer but don't work
- i only get left stereo

just wondering what's wrong here. i want to have the button to answer.

the only thing i can think so is the jack **** is no aligned properly

Any help would do