Under billing you can choose which payment option you want... 1 month, 3months, 6months, or 12 months. The more time you pay for at once, the cheaper the average monthly cost (assuming you wish to continue playing for the entire purchased time).
If you actually payed for 12 months, you should be golden for several more months, as SWG hasn't been out that long.
If it's been exactly a month, i'd check the credit card you used to make sure that there was a charge (and payment). It sounds like you got your free month (for buying the game), and then there was some trouble with your account/billing sign up or your credit card, and the charge or payment never went through (if your credit card expired or maxed out in between sign up and the end of your free month that could happen, as they don't put in the charge until your free month is over).
If you find that your card WAS billed, then you've got an issue with customer support... call them first, and if they don't remedy the situation within a few days, call your credit card company.