Most workers at my pizza store make the mistake of using their normal voices when calling out pizzas. When the story is full and noisy, that doesn't work at all. The customers won't hear you, especially if you're trying to reach a customer on the far side of the store.
What I do is shout from my diaphragm, so my voice is extra-loud and can be heard everywhere. The way you do this is to fill your lungs with air, and speak from the bottom of your lungs. The idea is that it makes your voice deeper, so it carries farther. It's the same technique that you use in choir, to hold a note for a really long time. It's very similar to the projection technique that people use in theater. (I'm not very good at choir or theater, so I don't know the difference.)
So, I had a dumb idea! Could I make this a puzzle in my pizza delivery game? Like, the main character calls out pizzas, when a co-worker scolds them for not being loud enough. "You need to hold your breath, like you're singing a long note!" Cue a music puzzle, where the co-worker forces you to sing an annoying pizza jingle about five times, until you get it right.