The Commerce Commission is cracking-down on the prepaid phone card industry after complaints from customers.
The commission prosecuted two companies last year and has issued new guidelines warning the industry not to mislead customers.
The commission said one company has been fined $140,000 for failing to make it obvious there was a daily fee of 22 cents for using the card.
One customer had bought a $10 card, made a brief call to Britain and was then unable to use the card the following month because it had no credit.
The commission is telling companies they should provide a clear, all-inclusive price on the card so consumers can easily tell which deal gives them the best value.
It said that using fine print to disclose fees and conditions affecting the headline rate could breach the Fair Trading Act.
