Vodafone has admitted overstating the size and coverage of its mobile network over a period of almost two-and-a-half years.
The company today pleaded guilty at Auckland District Court to 21 charges brought by the Commerce Commission under the Fair Trading Act.
Seventeen of the charges related to claims the company made between 2006 and 2009 over the size of its 3G network, including those made in a ''broadband everywhere'' campaign that ran between October 2006 and April 2008.
The remaining four charges concerned the availability of a $10 ''free airtime credit'' offered to Supra-Prepay customers between May 2007 and September 2008.
Telecom laid a complaint with the commission in November 2008 after Vodafone claimed, in a Christmas catalogue available from its dealers, that it had the ''largest and fastest mobile network''.
A footnote, in smaller print, explained that the claim was based on ''W-CDMA network coverage''. Telecom's mobile network at the time used a different technology, EV-DO. Vodafone's claim was repeated in mail-outs and on billboards.
Telecom said at the time it laid the complaint that it feared that people might be misled into believing Vodafone's network was superior to its own if they did not read or understand Vodafone's disclaimer. On an Auckland billboard, the disclaimer was printed in white on a partly pale background.
Each of the 21 charges carries a maximum fine of $200,000, meaning Vodafone could be up for a $4.2 million penalty when it is sentenced in September.
Vodafone was fined a total of $482,000 last year after it was found guilty of separate breaches of the Fair Trading Act, including not making it clear when mobile customers left its ''walled garden'' Vodafone Live service and could be charged for downloading mobile data, and failing to properly communicate the terms of a ''$1 a day'' mobile broadband offer.
Vodafone still faces one outstanding charge of misrepresenting the cost of its Sony Ericsson W200 mobile phone between July and August 2007.