...Yelling and calling them names is no good...
Very worth mentioning. I know in these situations it's hard to keep things civil, but if you think it through rationally, they'll be more inclined to correct matters as much as possible if they feel you're working with them.
On the other hand, they have to know they're in deep doo doo if they jerk you around. There is no way they did that and didn't know they were causing damage, so I wouldn't count on their integrity.
Speak softly, but carry a big stick.