When you sign up, we ask you to provide your credit card information. This information is used only to verify your identity and let us know you're not a robot. Your credit card is not charged during the verification.
When you signup for a paid account and after you have successfully verified your account, you will be redirected to the billing tab of Cloudalize where you'll be able to purchase the credits you need. Only then your credit card will be charged with the amount you have chosen.
You can learn how to change your credit card information here.