When dealing with someone on the phone, you could potentially jar them into being quieter by simply being loud and belligerent back. If they're on a business call and need to keep up professional appearances, having someone loudly bark "SHUT THE **** UP" or simply shouting embarrassing phrases directly into their microphone might shock them into being quieter as they need to apologize/clarify to the person on the other end. Similar to how your friends might have screwed with you while you're on the phone in school.

YMMV on reactions, however.