This won't happen often, as we have next to no substitutions. If it does happen, we'll choose something very similar to the original item, and send you a text letting you know about the change. You'll also be able to see the exact price, and a picture of the substitution, on your receipt in the app.
The price you pay will be the price of the new item you receive, including any offers. If the original item you ordered was on offer, we'll match that discount on the substitution. You can also hand the substitution back to your driver if you don't want it, and we'll remove it from your final order total.