Phone services have been restored after a mass outage that affected landlines and Eftpos facilities, from the Bombay Hills south of Auckland, to Northland.
The fault intermittently affected 111 emergency calls, homes and businesses.
A Telecom spokesperson says the company still does not know understand what caused the two-hour fault, and many staff are looking into the problem.
The company has apologised for the inconvenience.
Police Northern Communications centre, based in Auckland, says emergency calls were diverted to other centres for a time.
Many businesses say they quickly felt the impact of the fault, with some in the suburb of Mt Eden having to resort to old-fashioned processing of sales.
Some cafes were left empty, and one business owner says sales fell by about 40%.
Auckland's largest taxi operator, Co-op, reported difficulties.
Mobile phone services were not affected.