NATS4 GXBill
From TMM Wiki
Please don't test your biller setup with NATS4 GXBill's test account—it won't work correctly.
Setting up on GXBill's Website
Register a GXBill account. Record your GXBill Merchant ID and password. Setup your sites; for each site, record its GXBill Site Code.
Set the password script to:
Replace linkdomain with your linkdomain.
Set up GXBill in NATS
Go to the Billers Admin, select GXBill from the drop-down, and click Add. In the ID and password fields, enter your GXBill Merchant ID and password.
Go to the Sites Admin, edit or create a tour, and go do the Biller Details section. In the Site Code field, enter a GXBill site code. If GXBill gives you a Type you can enter it in the 'Type' field in the 'Biller Codes' column.