After logging in, select the area (city) to which the phone number belong and then proceed further.In the option "Search by" , select Telephone number. select the station to which the phone no. belongs and finally write the phone number in the "Search key field" . In this way the address of that particular number will be traced.
For selecting any other state of , log on to http://www.bsnl.co.in/index.html . In the Right hand side you see the "BSNL units" option (above Username field), select your state from the menu and then proceed further.
NOTE : Try both, number including (2) as well as number excluding (2) as a prefix.