Tens of thousands of Atmos Energy customers were charged 10 times the amount of their bill on Monday.
The billing glitch affected 39,000 customers signed up for automatic payments in seven states, including Texas.
Atmos withdrew $646.40 from Melissa Alexander's account instead of the actual amount of $64.64. The error led to an overdraft on her account.
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"My bank says, 'We're getting calls from other Atmos customers with the same problem,' and there's nothing they can do, so that's where my frustration was," she said.
In a statement, Atmos Energy apologized for the error and said it would reimburse any overdraft fees caused by the error.
Atmos sent Alexander an email at about 5 p.m. that said it would reimburse her for the overcharged amount, as well as any overdraft fees, within 72 hours.
"I put my faith in them doing automatic billing," she said. "They entice you to do that because it's convenient and all that. This is not convenient."
Alexander said she does not plan to continue to pay with automatic withdrawals.
"No, I'll log on and pay my bill myself," she said.
Alan Driggers said $347.40 taken out of his account Sunday night, instead of 34.30, the amount of his actual bill.
"I've seen some other folks, their bill might have been $80 or $100, and they were charged $800 $1,000, so I guess, in the scheme of things, $347 is better than 1,000," he said.
Atmos Energy said the glitch was an isolated error caused by one of its vendors.
Most of its customers' accounts should be back to normal in the next 24 hours, the company said. As of 3 p.m., all but 668 of the overcharges had been reversed.