Four leading telecommunications companies have received warning letters from the Commerce Commission over misleading practices.
Spark, Vodafone, 2degrees and MyRepublic have all been told they've breached the Fair Trading Act in different ways.
However, under current operating procedures a prosecution was unlikely if the companies amended their practises.
The letters follow comments by the commission that the complexity and range of telco goods and services can easily be confusing to consumers.
"The telco sector continues to generate a high volume of consumer complaints, despite previous compliance and enforcement work," Commissioner Anna Rawlings said.
The commission said Vodafone made misleading claims about "free" goods and services in a 12-month broadband plan.
In fact, to receive the "free" goods or services, the consumer was required to pay additional fees or to take additional services.
In some cases, a monthly headline price was advertised, but that price did not include the additional fees to be paid in order to receive "free" goods or services.
The commission said Spark was warned for saying Vodafone's 2G network was closing imminently, in the marketing of its Skinny Mobile service.
And it said Two Degrees made misleading representations about the price of its unlimited broadband plan by not identifying or inadequately disclosing the additional cost of a modem and its delivery.
MyRepublic was accused of promoting its one-gigabyte-per-second service up to 2 months before it was actually available.
It also said that customers on its gamer broadband service would not experience lag or latency when it could be caused by third party servers.
It also misrepresented the rights of consumers to cancel a service.
The latest letters follow a series of actions taken against telecommunications companies by the commission.
Trustpower was fined $390,000 in September 2016 for misleading consumers over the price and terms of its bundled electricity and unlimited data broadband offer.
In the same month, Vodafone was fined $165,000 for false price representations on invoices for its 'Red Essentials' mobile plan.
Vodafone also reached a $268,000 settlement with the commission in January 2014, over the promotion of its 'Broadband Lite' service.
Call Plus Services Limited, trading as Slingshot, was fined $250,000 in December 2013 over the telemarketing of its services.