Green mountain energy Scam, want me to pay them $500 or they will try to shut me off Astoria New York

I sign up for two year with green moutain and my bill was always 10.25 cents a kwh but now they change it to 23.45cent a kwh i caaled them and ask why and to cancel bc i never agree to that and the on,y lady that works there said well we are loosing money to keep your power on so we have the right to change the amount anytime to say in business. i said hell no you need to let me know and i have a agreement sign, she said sorry you cN cancel bc you are mean and upset so if you dont pay $500 on top of the bil we will send someone over and cut you off, i flip out called coned and they took over my acvt but green mountain block them and im still getting charged 23.45 cents but coned is charging me normal commerical rate and i have two enegry supplyer.. My normal bill goes no more higherthen $250 in the summer my bill is now $900, Please someone Help I cant Afford to be shut off its a Animal Clinic that need power to help save the lives of people pets..