"I wasn't aware of the iPhone 'Wi-fi Assist' setting until I called my provider 2degrees to ask why I was suddenly using so much data."
After turning the function off, Burns' data usage returned to her normal rate.
The Avondale resident said "I don't think the Wi-Fi Assist setting should be on by default, I understand the premise behind it is to ensure optimal service however since having the setting off there has been no noticeable degradation to the speed of my connection."
She says the first month before she realised the setting was on she probably spent an extra $80 on four data packs.
One Vodafone user, who asked not to be named, said she was shocked when she realised her data began to disappear within a day of buying a new iPhone but was able to stop it when she researched online and found out about the feature.
Craig Young from TUANZ (Telecommunications Users Association of New Zealand) told the Herald "It's an example where the maker of the phone has made a decision that isn't overly user friendly.
"It's okay in countries where you might be able to get unlimited data to your mobile device and it doesn't matter how much data you're chewing through but particularly users in New Zealand who might be on prepay or on smaller plans and are carefully managing data may find it's actually being sucked up."
He said his advice is that users should be looking at that and turning the setting off.
The Herald spoke with representatives of ISP's (Internet Service Providers) to find out how the software update has impacted customers.
A representative from Vodafone said the telecommunications provider was first made aware of the 'Wi-fi Assist' feature in September last year.
She said "At the time we alerted customers through our online forums and social media and we responded to several media enquiries. This affected iPhone users globally. As part of our response, we pointed customers to a page on our website which offers a step by step guide to switching the feature off. Our customer care teams are aware of the feature and proactively support our customers to switch it off."
A Spark representative told the Herald they don't have any control over third party apps or operating systems, many of which use data.
He said "We want to encourage people to use the tools that can protect them from accidental over data use or a feature or an app consuming more data than they were expecting."
He urged any Spark users suffering from data usage issues to get in touch.
2degrees spokeswoman Lenska Papich said "If contacted by customers about data use we work through a range of possibilities with them, one of which for iOS 9 users is to turn off the Wi-Fi assist option."
Apple responded to the Herald's enquiries to find more information through their support page, which can be found here.
How to turn off Wi-Fi Assist
To disable the function go to Settings -> Cellular and scroll all the way down and de-select Wi-fi Assist.
This screen also outlines which specific apps use data the most to make data management more monitorable.
