World of Warcraft Burning Crusade download question?

started to play Warcraft with the trial and online update so for actual game with it, I got a free month of game. I recently updated in line again for The Burning Crusade, and my question is: How can I get one month free? The last time I checked my account on the site has not yet shown the operation, but now I connect, said prepaid time is up.

To prepare, you get free time to update any extensions, and it will probably for a future expansion.

World of Warcraft: The Burning Crusade – Cinematic Intro