I was thinking along the same lines as you, Wendi, but the Fair Debt Collection Practices Act (15 U.S.C. § 1692, et seq.) only applies to consumers, which the statute defines as "any natural person obligated or allegedly obligated to pay any debt".  I'm no lawyer, but I didn't see anything in the statute dealing with business-to-business collections.  Individual states may have regulations that govern such communications, so your advice to Rob to be careful is wise, nonetheless.

Regards,
Scott Perry