Would you continue to use this company...?

I had that problem with an after market supplier one time. Trouble is if you drop them they come back to see why you dropped them. Call his company's head quarters and ask to speak to his boss. Tell the boss you have what you need from their company and would appreciate no more visits and interruptions from field salesmen. Throw in there that it's effecting your productivity in a negative way. They'll get the salesman straight for you.