He regularly treats individual participants enrolled in Defendant Daimler Trucks North America LLC Group Health Plan (" Plan" ). Healthcare providers who participate in the Plan are paid directly by the Plan; non-participating providers are typically paid by their patients, who must then file a claim with the Plan for reimbursement. Metcalf does not participate in the Plan. Instead, he makes the following arrangement with his patients: They assign their right to reimbursement directly to Metcalf and authorize him to pursue their claims on their behalf, as well as any other rights they have under the Plan in connection with his services. Both patient and provider benefit from this arrangement: Metcalf's patients get treated without having to pay out of pocket, and Metcalf streamlines his cash flow.