That simple question may not get you very far. Lots of companies are now implementing policies to not give out that type of information.

"Does Mr. John Smith still work for your company?"
"No, he is no longer here"
"Can you tell me who replaced him?
"I'm sorry, we can't give out that information"

This policy is being put into place by many companies to 1) stop telemarketers 2) stop headhunters 3) stop corporate espionage. (no, I'm not kidding about #3)

You're going to need to train this person to ask the right questions and how to get through to the correct person.

>Customer service implies that the person has to know or learn something about the business. I need someone who can dial the telephone number and ask "Does Mr. John Smith still work for your company?". If no, ask "What is the name of the person who replaced him (or got this job now)?" That is all.