Vodafone New Zealand has been fined $NZ960,000 ($A756,054) for misleading its customers in three advertising campaigns.
The company was sentenced on 21 charges, brought by the Commerce Commission, in Auckland District Court today.
The charges related to three campaigns run by Vodafone between October 2006 and February 2009 for mobile phone and broadband packages, which were found to breach the Fair Trading Act.
During sentencing, Judge David Harvey described Vodafone's conduct as "gross carelessness".
He said the company's Broadband Everywhere campaign was "clearly false and misleading" and that it had done "significant harm".
Commerce Commission competition manager Stuart Wallace said that before charges were brought against Vodafone in 2009, there were a significant number of complaints from the public about Vodafone's advertising campaigns.
"At the time, mobile data and phone packages were relatively new to the market. Customers have no easy way of verifying the claims being made for products like this," he said.
"This case reinforces that companies need to be especially careful that their marketing materials for new products are not likely to mislead."
Vodafone was also fined nearly $NZ500,000 ($A393,778.30) in 2011 for six other Fair Trading Act charges.