How do I turn off "Find my iPhone" on my device without wi-fi?
You can restore your device by putting it in Recovery Mode first. This will restore your device regardless of settings on the device, including Find my iPhone.


Turn your device off.
Hold Home as you connect the USB cable until you see the following screen:


You should see the following message in iTunes:


  iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes.

Restore the device in iTunes.