[derekmhewitt]

Obviously YMMV, but my personal take on this is that no particular fish is too big to be thrown back, especially if they're a pain in the ass.

That said, it sounds like you don't want to do that. So instead, if I were you, I would attempt to find a back channel to get the information you need. This could be the executives administrative assistant/secretary, a corporate public information officer, someone in their marketing department, etc. Basically anyone other than the obstructionist person you're currently talking to, but avoid going over their head (if they aren't the business owner). This requires more leg work from you, but could net you most, or all of, that future business if you can deliver where others would have given up. Don't forget to bill them for the additional hours you spend though, never work for free.