About trial subscription

So I purchased the original World of Warcraft off the website, and just downloaded it instead of waiting for the mailed copy to come in. Well I entered my card number in and everything assuming it'd pay for a month subscription, but instead I'm stuck with the trial version for like a month. And I didn't want that, because of how much less I can do. Is there any way I can cancel the trial version and just pay for a month subscription? Thanks for the help