Note that the device must be turned off to disable the feature.
The simplest and most convenient way to disable Find My iPhone on your device is by using iCloud.com. You can access your account from any browser on any device or computer. Head to iCloud.com, log in, and then follow these steps.
If you happen to use another iPhone/iPad with the same apple id, you can use the Find My iPhone app on it to disable your other device. In this example, we’re using an iPad.