Car rental giant Avis has been forced to refund 20,000 customers in Australia, thanks to a young mother's persistence.
She successfully complained to the competition watchdog about hidden charges, and now other companies are on notice.
Sue Fitzgerald expected to pay the price she was quoted on the internet when she booked her rental car.
"They told us the price was higher than the price that I'd booked," she says. "I thought, 'I don't think that's right – you have to charge us what we agreed to on the internet price.'
"And they said, 'No, you don't understand, that's just the way it is."
The hidden charge was only $10, but Ms Fitzgerald decided to act anyway, and wrote to the competition watchdog – and won.
"I think I was the only one that complained," she says, "so one little letter… and success for 20,000 people."
Avis was forced to issue an apology, and refund customers who'd paid the extra fees.
Avis declined to comment on how much the blunder would cost them.
3 News / Channel 7