Thanks for the reply Dave. I tried a lot to search the internet, find answer in the manual but no luck (Or may be my novice approach is not letting me see it)
I don't know if my questions depends on the model of the modem (I may be totally wrong). I choose this model as Araati made one SMS switch based on this modem, So I thought of starting it with this modem only as it will be easy to get help when needed. The datasheet of the At commands of this modem is: http://www.xmyn.com/jiuzhan/upfile/200711148574975767.pdf

Hope to get some constructive help soon.