How to use subscriberCellularProviderDidUpdateNotifier
<p>I have done something like</p>

<pre><code>CTTelephonyNetworkInfo *networkInfo = [[CTTelephonyNetworkInfo alloc] init];
networkInfo.subscriberCellularProviderDidUpdateNotifier = ^ (CTCarrier * carrier) 
{Do some stuff here
};
</code></pre>

<p>to get the notification when the cell service provider changes and do some tasks.The documentation says:</p>

<blockquote>
  <p>A block object that is dispatched on
  the default priority global dispatch
  queue when the user’s cellular
  provider information changes. This
  occurs, for example, if a user swaps
  the device’s SIM card with one from
  another provider, while your
  application is running.</p>
  
  <p>To handle changes in cellular service
  provider information, define a block
  in your application and assign it to
  this property. The block must be
  implemented to support being called
  from any context.</p>
</blockquote>

<p>I am not sure where to implement this in my code and will it exceute if my application is running in background or suspended. </p>
