How do I remove my credit card information from iTunes?

How do I remove my credit card information from iTunes? The instructions at http://www.apple.com/support/itunes/ are useless. They say:

To update your name, billing address, or payment information, follow these instructions:

1. From the Apple Account Information page, click the Edit Payment Information button.
2. Edit the information that you would like to change.Note: The payment methods that the iTunes Store accepts can be found in the payment type section. If you do not want a payment method on your account, select None in the payment type section.
3. Click the Done button once you've updated all of your information.

The problem is there is NO "None" option to choose and the page does not allow you to erase the current information. Apple apparently also does not have customer service or support people that answer the phone. Any help?

thanks,

John