Log into the Customer Area and below your details, you will see the "Auto-Rebill" option. Click "update" next to it, after you have logged in.
Invoices generated for you will be automatically paid using these card details.
Please note that before saving these details we will send a PREAUTH request to your bank to check the card's validity. This will NOT charge your card.
To update your repeat billing details, the easiest way is either to "credit" your account (this can be anything from £1 & will put towards your next invoice), or pay an invoice before your repeat billing date. Whilst doing this, enter your new card details & tick the "Enable Auto-Billing" checkbox.
Your details will be updated & no more bills will be raised on your old card.
All of this can be done from the "Invoices" or "Credit" sections of your Customer Area.