The Commerce Commission has laid 10 charges against Vodafone New Zealand under the Fair Trading Act for billing customers after their contract had finished.
Vodafone has labelled the issue a combination of unintentional system and human errors – which it says have since been resolved.
The issue, which covers the period from January 1 2012 to January 2017, saw a group of broadband customers charged for Vodafone's services to the end of a billing cycle despite having given notice that they wished to terminate their service earlier.
Russell Stanners, Vodafone chief executive, said the billing errors were unintentional and the company were disappointed by the Commerce Commission's decision to prosecute.
"We have had an ongoing dialogue with the commission throughout their investigation, and they have acknowledged our cooperation," Stanners said.