NATS4 Upsell Supported Billers
From TMM Wiki
Some billers in NATS4 allow your members to perform upsells, which allows your members to upgrade their account to a more expensive option on your join form. This can be configured through the Upsells Admin.
The following text provides a list of all billers who support upsells in NATS4, as well as a link to their biller-specific wiki article.
For more information on configuring an upsell in NATS4, please see our NATS4 Configuring Upsells wiki article.