Question

How can we switch off notification from device?

Answer 1

Remote (Push) Notifications

If you are talking about remote (push) notifications, you can unregister for remote notifications using the - (void)unregisterForRemoteNotifications method in UIApplication (see the class reference).

However, Apple notes that users can disable push notifications on their own:

You should call this method in rare
circumstances only, such as when a new
version of the application drops
support for remote notifications.
Users can temporarily prevent
applications from receiving remote
notifications through the
Notifications section of the Settings
application. Applications unregistered
through this method can always
re-register.

Local Notifications

If you’re talking about local notifications, you can use the - (void)cancelLocalNotification:(UILocalNotification *)notification or - (void)cancelAllLocalNotifications methods, also on UIApplication (see the class reference).