If you don’t want to be charged again:
To remove your payment method completely, you’ll need to cancel your subscription first. While a subscription is active, a payment method must stay on file. After canceling, you can remove your card, and your account will remain active until the end of your billing period without further charges.
If you want to use a different card:
To replace your card with a new one, you don’t need to cancel. Just add your new card in the Payment Method section, set it as default, and then remove the old one.