You must hold the line, no matter what. Don't let go, or you'll never get through. It's like a phone cord, but for your ears.
Note: Do not try this at home. Or do. We're not your mom.
Speak at a volume that would shatter a glass, but not so loud it shatters the glass. You know, just to be safe.
Practice your yelling with a friend, family member, or a poor defenseless phone battery.
When in doubt, just shout: "I'M HERE TO ORDER PIZZA! I WANT TO TALK TO THE PERSON WHO OWES ME MONEY!"
Don't be like that guy who just says 'uh-huh' to every question. Answer the question, or at least feign interest.
Don't be like that guy who just won't hang up. You're not getting any younger, nor are you getting any more popular. Just hang up.
It's not like you're still waiting for your ex to call you back.