If you are an iPhone user and are wondering why your phone bill has skyrocketed after upgrading to iOS 9 despite not using much data, we may help you understand the problem. It is not a bug but one of the features of Apple's new operating system that may have been eating up your phone data without your knowledge.

Most tech-savvy iPhone users will check new features once a new firmware is installed but many may not even care or feel the need to do so. But the fact is that some simple features can enhance your phone and some can create a mess if not set right.

The recently released iOS 9 comes with several new features that can boost user experience but there is one feature called "Wi-Fi Assist" that is turned on by default when a phone is updated to the new iOS 9. Apple might have done it with good intention to ensure that users stay connected when WiFi signal is weak but it can eat up more data.

"Wi-Fi Assist" feature automatically switches to cellular if WiFi signal is inconsistent, which means you may end up using more data than you are used to. So, to ensure that your data usage doesn't exceed your monthly plan, this feature has to be turned off.

Here are four simple steps to turn off "Wi-Fi Assist" feature in your iPhone:

[NOTE: It is only for users who have upgraded their phone to iOS 9]

Step 1. Go to phone setting >Choose cellular menu.

Step 2. Stroll to the bottom of the menu where you will see "Wi-Fi Assist" option.

Step 3. If "Wi-Fi Assist" is on, turn it off.

You might have solved the issue and your data consumption should be back to normal.