Yay more monkeys on the radio domestic.
In all seriousness if it's actually a problem in flight, I'll talk to a guy about it. Usually something like, hey man, you notice how you have to repeat yourself 6 times before ATC understands you? That's because they have no idea what you're saying. You're using a lot of non-standard phraseology.
Nothing worse than an American carrier checking in to Shanghai when they're busy. They can't handle more than 1 aircraft at a time as it is and now you might as well be screaming into the mic and flinging poo at him for all the sense you're making.
Also terrible is the moron at LAX or JFK when it's busy and can't use proper phraseology causing the controller to repeat himself endlessly, clogging the frequency, airplanes are missing turns because there's not time to give vectors and hold your hand through how to use a radio on an airplane.
Be a professional. Talking on the radio is supposed to be mastered before the ATP.