Reliant Energy over charged for services by $400 for one month houston, Texas

I had been with Reliant for over 5 years and had no problems. Then sept of 2008 I received a bill for $400 over the amount it should have been by past use. Had a meter reread it was off but not much in my favor.

The next month I had received a bill for $1200 when it should have been $200. I had another meter reread. It was right? Reliant customer service even thought it was kinda high but blamed the increase on a faulty appliance. I had the house checked out. No problems found. Had another company which is used by the state as a party to check the equipment. They found no problems but did change out the meter anyhow?

I was on auto pay so had to pay both bills. Was also in Iraq renting the house to a friend I had them pay me what it approx should have been. The house is energy efficient everything and summer bills should only be $200. Even less when I am there I don't use too much a/c.

I changed companies and the bill went back to normal but there was also a new meter installed. So one of the 2 were bad?

I would be willing to take  this to court could be grand theft?