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I see you are paying your subscription through PayPal, so if you want to change your Credit Card, you should do it on PayPal, also if you want to change your Payment method and pay with your Credit Card directly rather than with your PayPal account, you can follow this guide : http://www.jotform.com/help/330-How-to-update-my-subscription-s-payment-method
Hope this will help you.