If you're the kind of person who routinely uses almost all of the mobile data included in your monthly plan, there's something you should know about Apple's latest iPhone software.
What Apple's new iPhones and iOS can do
When you've got your shiny new, or at least newly iOS 9-enabled device sitting in your hand, what apps should you load up? We've got some ideas.
A new feature called "Wi-Fi Assist", which is turned on by default, has reportedly been quietly eating through users' mobile data quota while they thought they were on Wi-Fi.
The feature is designed to make sure users get a smooth online experience, switching automatically to mobile data to boost your connection speed if your Wi-Fi connection is determined to be too slow.
It's easy to see how this could be handy if you're trying to stream audio while walking away from your house, or browsing the internet in your backyard right at the edge of your Wi-Fi's range, but it comes with a downside as well.
For those who already use up most of their data plan while out and about, the feature could potentially blow out phone bills across the country, as iPhones pilfer mobile data at home to assist with flaky Wi-Fi speeds. Some users have already taken to social media to complain their mobile data usage has skyrocketed since they upgraded to iOS 9.
Those using the internet on a budget would appear to be at particular risk of bill shock, as in Australia low-cost mobile plans are notoriously stingy with the data allocation, and low-cost home broadband notoriously poor in its consistency.
Thankfully there is an easy fix, as the feature can be switched off in settings.
To make sure the feature is turned off, open the phone's Settings app and select 'Mobile Data' (it's called 'Cellular' on American phones). The setting for "Wi-Fi Assist" is below the app settings and statistics.
Of course if you generally find yourself swimming in extra data allocation at the end of each month, or frequently find your phone clutches on to your home Wi-Fi well beyond the point of being useless as you walk down the street, this feature could be a great way to avoid buffering.