Hello NatashaMne,
Just to clarify, are you referring to your cellular data or Wi-Fi? If you're seeing more usage than expected for your cellular data, you can turn it off for specific apps.
"To turn cellular data on or off, go to Settings, then tap Cellular or Mobile Data.
You can turn cellular data on or off to limit apps and services from using the cellular network to connect to the internet. When cellular data is on, apps and services use your cellular connection when Wi-Fi isn't available. As a result, you might be charged for using certain features and services with cellular data."
You'll find more information here: Use cellular data on your iPhone or iPad
Cheers!