If you subscribe to The Stock Butler directly with your credit card you can modify your payment information into your user profile by clicking here or click on the "My Account".
For your user profile, you can update your credit card information and then save at the bottom of the page.
IMPORTANT NOTE: Please note that it is possible that we may have to redo your payment subscription is the payment failed too many times. This is a security mesure that we are not controlling.
If you subscribe with your PayPal account, please have a look at this article.