Log in to your customer account. From the My Account page, click Manage Subscriptions to view your active and paused subscriptions. In the Payment methods tab, you'll find the current method of payment along with the current billing address. Click on the Payment method you would like to update, a dropdown will appear, click edit payment method and update the billing address details.
If you need to add a new Credit/Debit card, click Add new payment method.
*Please note, this is not the same as the shipping address. You would edit the address in this section if your billing address has changed.
Note: If you signed up using PayPal and want to change your payment method in PayPal, you need to cancel the subscription and start a new subscription via the checkout. This is due to PayPal requiring a new billing agreement for any changes made.