If you are paying us through PayPal (which you are, unless you paid for a whole year upfront) --- then you need to change any account/payment information with them. Just log into your PayPal account and make the necessary changes.
One thing to note: Sometimes PayPal cancels people's account when they change their account info. We don't know why on Earth they would do this, but it happens... If this should happen to you, however, never fear. We will not take down your website. You will simply receive an email from us letting you know that PayPal canceled you and providing you with an easy link to resubscribe.