Sales Meeting Pivoted into Speaking Gig on Unrelated Topic

My company, a biz intel startup, pitched to a prospect a few months ago, and they asked us to come back and pitch at their annual conference, when all the decision makers would be available. Seems odd, but okay. A week before the conference, no one had contacted my team regarding time or place, so I reach out. Yeah, we're already on the schedule and the topic has changed. Also, we're no longer allowed to pitch, and this is an internal sales meeting now. Again, strange, so I try to redo our pitch deck into a more informational one. It can't be done. I contact the prospect and tell them, "The topic you've given me isn't one I normally speak on, and I'm not comfortable with how this presentation is turning out since I've only had 48 hours to work on it." They reply saying that they don't care and want us to present anyways, then close it with, "Does that seem hard?" Now the internal sales meeting is tomorrow, no decision makers are attending, and I'm not allowed to pitch like was originally discussed. Moreover, they're not paying me to speak, but they want me to disclose my company's internal processes to help their sales team sell to our contemporaries. I don't know how to handle this. Any recommendations?