If you do not want your credit card automatically charged, the easiest thing to do is to remove your card from your account.
You can always remove saved credit card information yourself.
Please login to your account area: Billing -> Manage Credit Card -> Delete Saved Card Details.
If you want to leave your credit card information on the account, but you don't want it to be charged automatically, you must change your default payment method to PayPal.
In your client area click the green "Update" button on the left, then on the following page select "PayPal" from the "Payment Method" drop-down menu. Save changes.
Your licenses will now have PayPal as each of their default payment methods.
If you pay for any license with a credit card going forward though that license will switch the payment method back to credit card, so you must adjust it again to PayPal.
(Currently the addons for the owned licenses must have their default payment method adjusted manually, and will not be affected by changing the overall account default payment method.)