Consumer watchdog the Commerce Commission is now suing the company under the Fair Trading Act for breaches of consumer law.
Vodafone received 298 consumer complaints - the second largest amount taking into consideration complaints from last year and the first quarter of this year, many referring to billing issues with allegations of account errors and disputed charges over data use charges.
There were complaints about early terminations charges of contracts, late payment fees and the accessibility of contract terms and conditions.
Other complaints were for credit management, poor customer service, misleading claims about its ultra-fast broadband "Fibre X", recurring faults and network performance.
Vodafone told the Herald it was disappointed to be on the Commerce Commission's list of the most complained about companies.
"Our number one business priority is to improve our customer service," a spokeswoman for the telecommunications provider said. "We really care about our customers and want them to have a great experience, so we take this to heart. More than that, we have taken practical steps to move the dial."
The spokeswoman said Vodafone had last year appointed Helen van Orton, a customer operations director, to improve its customer service.
"In her first year in the role, changes to our customer experience approach have seen year-on-year complaints drop more than 50 per cent," she said.
"It matters to us when our customers are unhappy, and we are committed to continuously improving the experience our customers have."
Third on the list of the most complained about retail companies is Spark.
The telecommunications provider formerly known as Telecom received 256 complaints, 130 complaints more than Foodstuffs which operates supermarkets New World and Pak'nSave.
Spark complaints were similar to Vodafone's, largely about billing errors and disputed charges, contract terms, poor customer service and network faults.
There were also complaints and allegations about its sales tactics, including exaggerated benefits and misleading pricing, similarly to complaints about Vodafone.
Spark said the number of complaints about it were significantly lower to other companies.
"We believe that relative to other New Zealand businesses, including telcos, Spark has a significantly lower proportion of customers who need to resort to formal complaint channels," a Spark spokeswoman said.
"This is borne out by the recent Telecommunications Dispute Resolution (TDR) quarterly report which showed that customers of some of other telecommunications companies were over five times more likely to complain to the TDR than Spark customers.
"All customer complaints are taken very seriously and the vast majority of customers have their complaints resolved simply by talking directly to Spark."
Rob Limb, chief executive of digital insights company Track, which recently put out its annual customer service report, said telecommunications providers often rated low for good customer service due to outside influences, such as reliance on the infrastructure that makes such services possible.
For example, if a phone line dies or internet connectivity drops, it's often the provider that gets complaints, despite this being outside the control of the company.
In Track's Customer Experience Index it rated telecommunications providers as the companies which needed the most work to improve customer experience.
After Foodstuffs, 2degrees and Woolworths, formerly Progressive Enterprises, ranked in fifth and sixth place for the most amount of complaints received by the Commerce Commission last year and in the first quarter of this year.
The Warehouse and online marketplace Trade Me were also on the list, receiving 65 and 58 complaints each, respectively.
Airlines Air New Zealand and Jetstar were also complained about - 90 about the country's national carrier and 35 about Jetstar.
