Don't try to fool somebody
No matter how well you prepare, you may get stuck from time to time with objections you can't answer immediately. When this happens, it's best to respond in a straightforward and clear way.
Source: Sales consultant Wendy Connick
Prospects and customers generally feel better with an honest, "I don't know," than with a slick answer that has a hint of being wrong or a clumsy response that dodges the objection.