Answer: Agent.
Explanation: First of all we have to bare in mind the meaning of the words Rhetoric and Persuation. Rhetoric is the art of exposing, using the language to speak about a fact. Persuation is the ability to convince someone about something.
As regards with the question itself, there are different types of agents (travel agent, insurance agent, estate agent, etc) but in all of the cases the agent is a person who needs the rhetoric and the persiation to convince the costumer of buying or purchasing the product he/she is selling.