Give a specific example of how you or someone you know did not want to take no for an answer (cut back on quantity demanded), when somebody said "no thanks, I don't want to eat it", or "no thanks I'd prefer not to purchase it", or "thanks for inviting but I can't go out on Friday", and so on. The person insisting has inelastic demand and explain it as such. Don't forget to mention what entailed the higher price that the person insisting had to endure. Notice that this refers to human interaction and it has to be explained in those terms.