[officialtony]

Good Job. Not working for them is one way to remedy the problem. I would also let other umpires know the situation -in and out of your association. Let this school or organization try to find competent umpires after the word is spread that they don't honor their contracts. It may take some time, but the cost they experience in poor umpires who will work for them will substantially outweigh the money they DIDN"T pay you and your partner.
By the way. You did the right thing in suspending the second game.