Customers on the Ultimate package, can make a one-time payment to their account from the Billing -> Overview page of the RBLTracker portal:
When you click the “Add Funds” link, you’ll be able to select an amount to add, a payment method (either by credit card or by Paypal), and if you’re paying by credit card, the payment source:
Credit card payments will be processed directly; for Paypal payments, you will be redirected to the Paypal website to login to Paypal and process the payment.
The payment will be immediately placed on your account, and can be used right away.