Well, the situation would be this: you're trying to get the attention of some person you use the formal with, but they act as if they hadn't heard you (and maybe they haven't). You get a bit impatient or even angry. So you're saying this sassy sentence, but, yes, you'd still use the formal.
If you switched to informal just because somebody ignores you, it would make you look quite choleric. Normally, if you decide to aggressively rant at strangers (or e.g. an employee of yours) and call them names for e.g. spilling their drink over you, or (a waiter) overhearing your call at the restaurant, or refusing to stop whatever you don't like them doing (e.g. on the train), you'd still stick to the formal address.