I can't really comment on why they are doing this, as you didn't give any information about what happened, but the bottom line is that you have a judgment that was passed against you. It's too late to fight it; they went to court and a judge agreed that you owe them money. You should have received a notice for the hearing in the mail, and hopefully you at least went to court and tried to defend yourself.
Honestly, your only real options are either a) pay them what they want, b) get a lawyer to help you, or c) take your cash, move to a different state, and open an account with a different bank, preferably something small and local. As long as they can find you, they can find your money.
Next time, try to fight harder before the judgment is passed, with a lawyer at your back.