Ok so I have a Sony Ericsson Bluetooth headset (similar to this one and a Nokia 6500S mobile phone. Why can't I use them together? Is it because it's not the same company?

P.S. I don't know if this will help, but this is a picture of a headset similar to the one I have:

http://www.phonearea.net/wp-content/themes/default/pictures/sony_ericsson/2008/q1/sony_ericsson_hbh_pv708.jpg