VX7000 and headset on/off button prob's

[BUmmedic]

Whenever I plug a headset with an on/off feature(button to answer/end/initiate voice dialing) into the 2.5mm jack and hit the button, it dials the last number in my recent calls list (basically acts as a redial button). Every other voice-dial phone I've had will respond by asking me "name please" when I press and hold the button with the phone on idle. I haven't tried to see if the button actually answers or ends calls because if it doesn't initiate VD, then it's no use to me anyway. Anyone else have this experience or problem and know of anything that can be done??? Thanks.