Your data usage is being sent to Apple in order to help Apple improve their products and services. This is done automatically. But I don’t think this is unsafe. Still if you want to turn this off go to Settings -> select General -> About -> Diagnostics & Usage. As shown in the below screen shot you can see that Automatically Send option is selected. When you tap Don’t Send option, your data usage details will not be sent to Apple. You can also check by selecting the link About Diagnostics and Privacy to read out more on this.