Symptom:
Phone hanged up.

Conditions:
Execution of following steps very quickly - 

====================
1) Press message key . 
2) Press keypad 2 (Visual Voice Mail)
3) Enter Pin and press SignIn. 
4) Press Exit . 
5) Press keypad 1 (Voice Mail) 
6) Press speaker (to end the calling to Voice Mail server) 
7) Press Keypad 2 (Visual Voice Mail)
 
Issue seen here , Above message box with two option ?OK? and ?Exit? will be displayed 
Here if we press Exit window will gray out but if we press OK , we do not face any issue.
=================