Negative test cases for testing
mobile phones:

1.removing the sim card and made a call 
2.by invalid phone number
3.made a call at which there is no tower signal
4.Made a call after removing the battery or at no power in 
battery and also we can add some more points...

The test cases written, are only one part of mobile testing
and just point no 1 and 3 may have some possibilities else no.

Ramya Nagendra please write in details u r looking for some
specific application point of view or the general mobile
testing, u may cosider the following points

1: Install the application (if specific to application) else
make some changes in ur  fone settings and take the battery
out forcefully, reinsert the battery and see either every
thing is working fine and the settings u have made are saved.
2: For camera application try to take pictures without
opening the camera shutter.
2: Send SMS and restart the handset before send complete,
see the message status in outbox.


Like this many cass u can generate by urself :D