Vodafone needs to spend less on flashy advertising and more on sorting out its service, says Consumer New Zealand chief executive Sue Chetwin.
Chetwin's comments come after the telco came in last for both mobile and broadband services in the latest Consumer NZ survey.
About three-quarters of Vodafone's broadband customers reported spending a long time on the phone waiting to speak to a representative with nearly half of those surveyed saying the service was poor when they finally got through.
"Vodafone was the only provider that rated below-average on all our performance measures – from customer support to value for money," Chetwin said.
The company also ranked in last place in the previous survey in 2017.
Vodafone customer operations director Helen van Orton said the company was disappointed with the ranking.
"We serve more than two million customers across the country and we take the satisfaction of each and every one extremely seriously," she said.
"We constantly benchmark our progress, and our own numbers show a 50 per cent drop in consumer complaints made to Vodafone year on year."
She said Vodafone was committed to determining a newer, more objective framework for measuring and addressing customer service issues across the sector.
Competitor Spark was also up for slow response times, coming in below average overall in the survey.
Consumer NZ said the "dismal" performance of the country's two largest telcos dragged down average overall satisfaction scores to 54 per cent for mobile providers and 49 per cent for internet service providers (ISP).
"Smaller providers returned better results than the big guys," Chetwin said.
"Best in show for mobile providers was Spark-owned Skinny, with a satisfaction score of 75 per cent. 2degrees also clocked above-average results, sitting on 61 per cent."
Vodafone rated 48 per cent overall with Spark only slightly higher on 49 per cent.
Flip was rated the top internet service provider with an overall satisfaction score of 70 per cent, however it didn't offer fibre.
Among ISPs that do, Skinny customers reported fewer problems than others.
The survey showed fibre was now the most common type of residential internet connection, although for many households the installation process had been difficult.
"One in three fibre customers encountered issues during installation," Chetwin said.
"Twenty per cent said agreed time frames weren't met, while 12 per cent told us their property had been damaged or not restored properly during installation."
Chetwin said customers who weren't happy with their mobile or internet providers had options and should consider switching.