Anniejohn, this topic is one of those details that piques my interest--and also ticks me off, at times, because sometimes people use different labels to spin a position.
I think what you call your staff members is up to you, and it needs to be endorsed by other people in the organization. If others in the organization don't use the same vocabulary, I take that as a sign of disrespect as well as ignorance--both of which begin with laziness.
An "agent" for me is a technical term you use when you are talking about a person that will receive a call in a contact center (a software term). And the software doesn't dictate what the person's job title should be; the software is a means to an end.
I like the word "representative" because I think of a person whose work involves responding to requests for some type of guidance as someone who "represents" what a company has to offer, and hopefully that is "excellence." Some people inject positive spirit into their job titles or department names and include the word "success" somehow.
I haven't been around long enough to be a great historian in work cultures, but my sniffer tells me that the word "manager" has become an option in the last few years as a way to empower employees who are not "managers of people" or "company managers" through a term that elevates them above connotations that are not desirable--much like how we seldom talk about "secretaries" and have moved on to terms that indicate how the secretaries of old were actually enablers of work completed for significant figures in a company, like a President or Chief this or that. Of course it all has to do with "status" and morale and respect in the workplace. Being a keeper of "secrets" (not literally secrets, but that's the word origin) sounds pretty significant to me, but "secretary" in an office (unlike Secretary of State) just doesn't cut it anymore.
Customer Service Representative and its acronym CSR can mean a range of things, as does Customer Service itself. Depends on the context and the audience. Project Manager is another term that gets used and abused (some people responsible for sales initiatives think of project managers as personal assistants; others see them as highly powerful people that bring together a number of people with different competencies toward a goal and ensure its execution).
If I could steer you toward a decision without making that decision for you (if indeed you want to name a job title), I would think of what the people in the role are going to do and which words would describe the result felt by the person/customer that got what they were looking for; and then find the best-sounding combination of words. It has to be a title that you will like to use when talking about your staff members.
I definitely think job titles can be a game in semantics, but I take them seriously as well, as they are names. | 
