Apple's latest iOS update may have great new features Tech Radar warns that it may prove costly for users with limited mobile data.

Wi-Fi assist, which uses mobile data if internet signal is weak, is enabled by default in Apple's iOS 9, which means that whether you like it or not, it will eat up your monthly data allowance if you're not careful.

Gizmodo writer Chris Mills has seen the data jump in the new system and he suspected that it may have been the Wi-Fi assist feature that's the culprit. "On the iPhone 6s that I've only been using for three days, my data usage is at 950MB; half of that is from Netflix, which I make certain to never use when I'm on the go. In fact, the only time I've used it in the past couple days was at home, using what I thought was Wi-Fi," Mills said in The Washington Post. 

So how do you turn the Wi-Fi feature off?

First, go to the Settings app on your phone and tap on Cellular (or Mobile) Data. At the bottom of this page, you will find a Wi-Fi Assist toggle, which you just need to switch off.

This trick is especially helpful when you have a limited data package and it is recommended that you turn it off before it racks up an enormous and unexpected bill.

The Washington Post also noted that from your Settings menu, you can also keep certain apps from using cellular data. The menu lists all your apps and you can decide manually which apps you will allow the use of cellular data. Turning some apps like Netflix off can cut down on data usage.

In order not to get shocked from data charges, it is also recommended that you use your phone's built-in counter that helps track the amount of data that you're using. On the "Cellular Data Usage" option of your phone's settings, you will see the estimate of the data you've used since you last reset the counter. If you're unsure how to do this, check the bottom of the Cellular menu and click on "Reset Statistics." However, to ensure your numbers are up-to-date you may need to reset your counter manually every month.

There are a lot of tips and tricks that you can use on your phone, check out the video from Tech Radar below to find more hacks on your iPhone. What do you think of these tips?