On the Payment processors page, you'll see that CCBill is turned OFF by default. This is because the fees are higher, but also because their approval times are longer for custom domain names.
Once CCBill approves your site, you are free to display it as a default payment option, or leave it as a backup payment system. As a backup payment system, it will only be used when payments fail with Segpay.
Payment processors can be turned on or off and reordered at any time.