A Telstra customer in Western Australia got the shock of her life when she received a bill for $465,595.23 this year.
Mum-of-three Karen told television show A Current Affair that she normally paid $400 per month for her family's internet and mobile plan.
Even if she went over the data limit, she wondered how it could physically rack up that much in surcharges.
"Has it been hacked? How has it actually managed to do that much data download without bursting into flames?" she said.
The problem was that Karen had trouble getting Telstra to acknowledge that the bill was a mistake.
She first called the support number with no success, so visited the local Telstra store in Bunbury.
A salesperson there said the enormous total was "absolutely a mistake" and blamed a flaw in the billing system.
But the next month, the bill had increased to $466,000 with the new month's $400 added onto the huge unpaid amount from the previous period.
The error was only fixed when Karen reported her situation to the television show, and Telstra consumer & small business executive Michael Ackland was shown the bill.
"We have confirmed with her in writing that all those charges are removed and she should ignore them."
He apologised "unreservedly" to Karen and said she "should ignore that bill" while the billing system sorts itself out.
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