How Do I Change My Credit Card Information For My Pro Account?

You actually do not manage your credit card information directly on
StageAgent. Instead, you will need to do this via your Google Checkout
account.  But it is super easy. To change your credit card info,
please do the following:

1) Login with your Google login info on Google Checkout:
https://checkout.google.com

2) Edit your default payment method. Remove the bad credit card and
input the information for the new credit card.