To add a credit card to your account, log in to Portal - http://portal.neural.net.au and follow these steps...
1. Select the "My Account" tab
2. Click "My Payments" on the menu
3. Choose "Add a Card"
4. Enter the card details
4. Click "Add Card"
Any invoices on your account will now be automatically charged to this credit card.
Automatic pre-paid account top-up:
You may also optionally configure automatic pre-paid top-up's by following this guide: