Police say more than 900,000 scam phone calls were made from one number in June and July asking people to pay outstanding fines using iTunes vouchers.
Detective senior sergeant Iain Chapman said the phone numbers made the calls appear to be coming from New Zealand, including those associated with Government departments and police.
But he warned that those agencies would never request fines be paid by iTunes vouchers.
"While these numbers may show a New Zealand number, they are in fact coming from overseas," Chapman said.
"We are seeing a huge numbers of these calls coming through, with over 900,000 calls showing as coming from one New Zealand number over the months of June and July.