Sarah Vs. the Morons

Me attempting to order pizza today:

Me: I have a coupon for one large specialty pizza and one two topping for $20.99
Papa John's lady: What would you like for those?
Me: I would like a Hawaiian for the specialty and a pepperoni mushroom for the two topping
Papa John's lady: I got the two topping but did you want the barbecued chicken or barbecued chicken and pineapple?
Me: I don't want barbecued chicken at all, I want ham and pineapple.
Papa John's lady: We can't do that
Me: Do you have ham and pineapple?
Papa John's lady: Yes
Me: Why can't you put them on a pizza?
Papa John's lady: We can't do that
Me: Can I use that as my two topping pizza?
Papa John's lady: Yes
Me: So I can do that
Papa John's lady: Yes, But you can't do that with your coupon. I can give you the barbecued chicken pizza for $17.99 though
Me: I don't like barbecued chicken
Papa John's lady: I'm sorry ma'am but you won't be able to use that coupon
Me: What if I did ham and pineapple for the two topping and a deluxe or supreme or whatever for the specialty pizza
Papa John's lady: That would be fine
Me: But I can't sub a cheaper pizza for the deluxe
Papa John's lady: No ma'am
Me: Whatever, I will do the ham and pineapple and a deluxe pizza then.
Papa John's lady: Thank you that will be ready in 30 minutes

I really don't understand...