iOS 9 users have been plagued with a bunch of inherent bugs and issues ever since its release, including the recently unearthed mobile data usage issue, wherein the upgrade is costing more data bandwidth usage due to a built-in feature that automatically switches between Wi-Fi and 3G/4G data networks to provide the best possible connection to the user at all times. It is reported that some users are experiencing a significant increase in data usage after iOS 9 upgrade, although there is no change in their browsing habits.

According to one Twitter user, Jim Ray, the data usage has increased from just a couple of GBs to 7GB after upgrading to iOS 9, and it is suspected that the WiFi Assist feature could be the root cause of this problem. Affected users who suspect that their data bandwidth is being wasted for no apparent reason can go ahead and try the steps outlined below to disable this automatic switch.

Here is how you do it:

  • Launch the Settings app and tap Mobile Data/Cellular
  • Scroll down to the bottom of the page and disable Wi-Fi Assist

That's it. Your iPhone will no longer switch automatically to 3G or 4G data network at times when the Wi-Fi signal reception is poor or weak, which should prevent unexpected and unwanted data usage.

However, you can still manually switch back to 3G/4G data network manually whenever the need arises. Furthermore, you can evaluate and keep track of the consumed mobile data bandwidth on your iPhone by navigating to Settings > Cellular > Cellular Data Usage.

[Source: Business Insider]