Beware of facebook credit pay later method

Today, several game applications in facebook offers a pay later facebook credit. This method lets you to enjoy all the benefit a facebook credit can offer. However, this method is quite tricky like a credit card. So if your not vigilant enough, you will be like me. Just recently, Im playing backyard monster in facebook. For aiming a higher level and speed, I explore the get shinny facebook credit. And I found this button the pay later button. I thought there will be corresponding question. But unfortunately none. So the moment I click the button. I automatically got a Created of $3.04. To avoid experiencing this kind of business, please be very vigilant.