More than 100 Telecom service workers have gone on strike in Auckland on Wednesday.
The technicians are among 900 workers Australian company Vision Stream wants to contract as owner-operators.
The Engineering, Printing and Manufacturing Union, which represents the workers, says they have had a gutful of Telecom and are determined to fight back.
Telecom's network arm, Chorus, says the workers fix landline faults, and install broadband and phone services - and those on strike represent about a third of its workforce on the North Shore.
Chorus says customers may experience some delays, but faults will be prioritised.
The EPMU says a union meeting on Thursday will decide whether to continue the strike action.