Oakbill
Please don't test your biller setup with Oakbill's test account—it won't work correctly.
Register an account with Oakbill.
(Note: you don't need to specify postback and return URL for Oakbilling; NATS dynamically sends the correct information during each transaction.)
For each join option you plan to offer, click Tools, Websites, Subscriptions and Prices, and Add a subscription. After saving, record its Subscription I.D. number.
Setting up in NATS
Go to Billers Admin, select OAKBill from the Biller drop-down from the bottom. Enter your Merchant ID, API, and Secret Key. You should have received these from Oakbill; if you didn't, please contact Oakbill support.
Go to Sites Admin, add or edit a site, enter a new join option or edit an existing join option, and enter the Subscription I.D. number in the OAKBill Product ID field.