In place of BSNL MOBILE you must write your own word. You can type anything but not more than 16 Characters.
Now save the file. Delete the old spn-conf.xml file from /system/etc and copy new spn-conf.xml file to system/etc.Reboot Your phone.After the reboot it show the old carrier but after 20 - 30 sec it shows the new name on the lockscreen.
spnOverride numeric="40480" is Mobile Network Code (MNC)+Mobile Country Code (MCC) code. Get codes for your operator and country from here.
Add actual code in spnOverride numeric and any name you want in spn.