How to know if my iphone is using my data plan?

How do i know if my iphone is using my data plan? Like when I download an app, does it use the data plan. I only have 300 MB. I don't have internet. I just use my Wi-Fi at my house to download apps. Will it charge my data plan if I download apps at my house on my Wi-Fi

Downloading apps, browsing web, using Facebook anything having to do with the internet uses data, if you use Wi-Fi to download an app, you will not use any data.

If you have the Wi-Fi icon on top, then you're running off just Wi-Fi. If you're still concerned, you can download the app Dataman, it tracks how much data and Wi-Fi the phone uses.

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