Businesses numbers are not eligible for registration on the DNC Registry, only residential and personal numbers. Therefore complaints to the DNC office about sales calls to business numbers are not acted on.
From the Information for Consumers page of the DNC website:
"Can I register my business phone number or a fax number?
The National Do Not Call Registry is only for personal phone numbers. Business-to-business calls and faxes are not covered by the National Do Not Call Registry."