Vodafone says some of its fixed-line customers are currently unable to make calls.
Neither fixed-line nor mobile customers are able to reach the company's call centre.
Spokeswoman Michelle Baguley said the problems began at about 6.30am.
Baguley said Vodafone was still investigating the cause of the problem, but there were a limited number of things it could be.
Vodafone has apologised on its website.
- The Dominion Post
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