Vodafone insists it won't be distracted by merging its business with TelstraClear after it received the green light for the $840 million takeover.
The Commerce Commission says the deal does not substantially lessen competition, with plenty of rivalry in the fixed line and broadband market.
Telecom will still dominate - with half the market - but the acquisition of TelstraClear gives Vodafone roughly a third of the market share, which analysts say gives it enough heft to challenge the incumbent.
Vodafone and TelstraClear will operate as separate businesses for the next six months and Vodafone chief executive Russell Stanners says the merger is likely to take at least another 1½ years to complete.
But Mr Stanners says it will continue to compete to attract and retain users. Competition is also coming from new quarters, such as Google and Facebook.