If the popup still appears even after you have tried to disable Find my iPhone, please follow the steps below to make sure it's disabled.
1. Please tap the Home button of your iPhone twice and end the Settings process. Now restart the phone.
2. Go to Settings>iCloud and make sure that Find my iPhone is disabled there.
3. Make sure your iPhone is connected to the Internet.
4. Use iTunes to back up the iPhone see if it works.
