See item 3 in the second set of links.
What To Do If Your iDevice Is Lost Or Stolen
If your iPhone, iPod, iPod Touch, or iPad is lost or stolen what do you do? There are things you should do in advance - before you lose it or it's stolen - and some things to do after the fact. Here are some suggestions:
3. AT&T, Sprint, and Verizon can block stolen phones/tablets
It pays to be proactive by following the advice on using Find My Phone before you lose your device:
2. Setup your iDevice on iCloud