inside salesman

noun2

1. •
   A sales representative employed by a retail or wholesale vendor who works on the premises of his or her employer, transacting with customers directly on a sales floor or by telephone, online messaging, etc.

   • I used to be an inside salesman. My job was to sell via phone and online, and to support several outside salespeople as well. — 2010
2. •
   Someone employed within the organization of a prospective buyer who serves (whether for good motives or not) as an advocate for a seller's product or service.

   • ASSISTANT COMPLEX . . . . doesn't have enough authority to buy. . . . Show him that your proposition will make him a star in the eyes of his superiors. Keep him as your "inside" salesman. — 1951