Xcel Energy Is trying to make me pay for their mistake Denver, Colorado

The meter at my residence went out and xcel energy failed to catch it even after we reported our bill being less than what it normally is. When they finally figured out the meter was bad, they replaced it and sent us a HUGE bill! After more than 10 conversations with xcel and three with PUC. Only in circles am I led by this huge company. I have been told at least
5 different stories about when they think the meter went out and I just wanted the facts. They also could not tell me if it was the gas meter or the electric meter. Now this has escalated into them threatening me because they can't come up with proper un-coded documentation. They are scheduled to turn off my power on 5/09/11. I am otherwise current with
my bill. The discrepancy is in the bill regarding their equipment failure. Now at this point they are BULLYING me by telling me they are going to turn off power and I will have to pay a fee in order for them not to turn it off at this point. And a bigger fee to re-connect. We offered to pay them $730 dollars which was a figure I averaged by researching 3 years worth of bills. They declined and told me that "I was lucky that I wasn't being charged back a whole year. HELP! what should I do?