(1) "Commercial telephone seller" or "seller" means a person who, in the course of such person's business, vocation, or occupation, on the person's own behalf or on behalf of another person, causes or attempts to cause a commercial telephone solicitation to be made; except that "commercial telephone seller" or "seller" does not include the following:

(s) Any telephone marketing service company which provides telemarketing sales services under written contract to sellers and has been operating continuously for at least five years under the same business name and seventy-five percent or more of its services are performed on behalf of sellers exempt from this section.
http://www.state.co.us/gov_dir/leg_dir/olls/sl1997/sl.188.ht...

Another alternative

Another alternative, although the one above sounds good to me. Here in the UK I think they would rather say telesales representative. Although I heard: telesales agent once, but to me it would imply of an agent that deals with telesales, namely employs telesale people.

On my time sheet (I used to work for Lloyds bank here as a telesales person) it says...Nature of assignment: TELESALES ADVISORS