Cellular Network ID
Hi,
according to hxxp://en.wikipedia.org/wiki/List_of_mobile_country_codes
your country is Nepal. There are international standard organisations that assign country code (or MCC). In early days of GSM in europe it was ETSI. Nowadays it must be ITU, but I am not sure. You have to check 3gpp.org, that is responsable for all UMTS and GSM standards now.
The Network code (or MNC) is usually given by telecom regulator or governement of respective country.
If the question is how does the phone know the MCC and MNC of a certain operator, the answer would be that each base station in the network is constantly transmitting broadcast channels (BCH or BCCH), that carry that information.
And as Artem says first 5 digits of the sim card number or (IMSI) are MCC+MNC. However the IMSI is kept inside the sim card, and the number you see written on the card itself has nothing to do with IMSI