Telecommunications company Spark has pleaded guilty to breaching the Fair Trading Act.
The Commerce Commission brought the charges against it in July for wrongfully charging customers, who signed up for broadband services and then left.
Spark said a small number of customers were affected by the system-based errors, which were genuine mistakes made with no malicious intent.
It said it had refunded all affected customers that it could contact.
Penalties for the charges were yet to be determined but Spark said the costs would not have a significant impact on its finances.
Meanwhile, Spark has also gone to court today to secure the branding for its new sports streaming service.
The High Court in Auckland has held a closed hearing on what is believed to be a bid by Spark to control the brand "Spark Sport".
Spark has applied to use the name as a trademark, but a business consulting firm Ynot Management owns the internet domain name, Spark Sport, until April next year.
Neither party would confirm the details.
Spark will start rolling out its service with English premier league football, Formula One motor racing and World Cup rugby from next year.