If you have a cool original idea for an article - just the sort of thing they publish then:-

Write your article, make a front page with just the title on, your contact deatils, and printed at the bottom:-
Firt Serial Rights

Don't hold your breath, but it shows you want to be paid.

If you're not bothered about being paid, phone up and ask what they want an article about. Explain you would like to make the first steps towards being publishesd and building up a portfolio. Have some suggestions. makes more sense than working your ass on something purely speculatively.

Take an interest in the magazine to the extent of reading a copy before setting out on this route.