Unlimited Plan users can update their credit card information:

1. Log into your account
2. Click on the "My Meetings" tab at the top
3. Click on the "My Profile" link on the left
4. Click on the "Edit" button at the bottom
5. Enter in your new credit card details
6. Click on the "Save" button

Pay-As-You-Go Plan users do not need to update their information since they enter their credit card information every time they add funds.