Chinmoy- Cell phone is a tool of empowerment for those who use it properly. What will be use of multi functional costly cell phone for a school going boy or even a businessman who only talks and does not even send SMS.
Deepti- You have rightly commented that cell phone is to communicate. So using a cell phone that meets your purpose is necessity and otherwise luxury. So, if you have additional features in your smart phone that you cannot or do not use, this is luxury.