Hello,

           Please see link below by Paul from Google, works
for 99.4 % success rate, only did not work for 6 people.

http://productforums.google.com/forum/#!category-topic/mobile/android-devices/S_oB-ELv2oY


       If you are seeing for emergency calls only! Call your Carrier for the puk unlock code.


      I won't tell you what if they don't work after this? Just yet but what you must try the link above first because you really don't want to know what must be done if that will not work, but should.

      Good Luck