Repeated cold calls.
This company continues to call and visit our place of business in spite of being told numerous times not to do so. Their last caller was typical: after I explained our position and told her that her company was on our "never do business with" list due their inability to simply listen to English, so even if she was selling something we wanted, which they don't have anyway, we still wouldn't be interested.
Care to guess her response?
"Are you the owner?"
Yeah. After flat out telling her we will never deal with her company, she has the abject brazenness to keep trying anyway. With a marketing strategy like this, there's little doubt that the actual product is worthless- if there even is a product.