My cell phone sometimes do not work my cell phone is a vri motorola i have been using it since a year and half ago , it still works but sometimes the operating system gets frozen and it doesn´t let me do anything , i think that i must format my cell phone so it can be fixed but really i don´t know sometimes on screen appears a messages saying "SIM card must be inserted " and the SIM card is already in so when that happens what i do is to reset my cell phone and sometimes it gets fixed by doing that