Eleven charges have been laid against Spark New Zealand today by the Commerce Commission.
It alleges Spark made "false or misleading representations relating to its billing and a $100 offer for new customers".
In a statement, the Commerce Commission said the charges were filed in the Auckland District Court after three alleged incidents.
These include customers being overcharged after a fault in Spark's broadband network caused a mis-recording of usage and an offer by Spark of $100 account credit for subscribing to a particular broadband plan that could only be redeemed by phoning Spark. However the Commerce Commission claimed it gave customers the impression they would be eligible for the credit if they signed up online.
The last charge claimed that from June 2, 2014, terms and conditions stated that Spark charges would end after 30 days if the customer gave notice to end their contract, but "the Commission alleges that the customer's final bill included charges for the entire next monthly billing period regardless of when the Spark service stopped".
Spark New Zealand made a statement this morning acknowledging the charges, and said that it had "already applied credits to the accounts of all impacted customers and, for former customers, [and] has made extensive efforts to return all money owed so they receive the benefit of their credit".
Spark’s managing director Simon Moutter said the incidents were "all system-based errors caused by genuine mistakes with no malicious intent involved on the part of Spark".
"That being said, we are deeply disappointed that these issues have affected our customers.
"These errors were for the most part an unfortunate and unintended consequence of some of the change we’ve been through and we regret that they occurred," Mr Moutter said.
"We have spent time learning from these issues, amending processes, updating training and staff resources, and we continue to work hard to ensure these kinds of errors don't recur in future. We have made every effort to ensure that customers have received all amounts owing to them and will continue to do so."