Pet Peeve

I absolutely hate when people pull their car in front of my LLV to stop me from delivering so they can come hound me about some check for an address that isn't even on my route (or to ask some arbitrary question that doesn't matter. It's usually for mail for a street I dont deliver to, though.)

What do you guys do in these situations? I usually tell them, "I don't have it, sorry," or "That's not on my route." Some start to get pissy and angry when I don't have their mail like it will magically appear in my hands. I obviously can't just run them over. 😅

EDIT: I am so very bad at being assertive and usually resort to being really passive in hopes that they don't yell at me, but it isn't helping. How can I tell them to leave me tf alone without getting fired?