Vodafone says that rival Telecom has failed to take elementary steps to prevent interference on its network, causing the company significant damage.
It's seeking an injunction at the High Court in Auckland to stop the launch of a new mobile phone network by Telecom on 13 May.
Vodafone says Telecom knew late last year that not installing filters on its transmitters would cause interference on the Vodafone network.
Vodafone lawyer Julian Miles QC says the new network is operating at only about 15% capacity at the moment, and damage will be much worse if the launch proceeds.
He says it's commercially unacceptable that Vodafone calls are being cut off, contends Telecom has breached the Radiocommunications Act and International Radio Regulations.