may charge an entity a flat service fee for the provision of services to such entity if such fee is set forth in an agreement between the pharmacy benefit manager and such entity. (2) Definitions In this section— (A) the term flat service fee means a flat dollar amount that is not directly or indirectly based on, or contingent upon, or otherwise related to— (i) a drug price (such as wholesale acquisition cost) or drug benchmark price (such as average wholesale price)