To transfer balnce in your bsnl prepaid mobile is very easy.to transfer your balance to your friends follow these steps and you will succeed.
Balance Transfer Trick for BSNL Prepaid-
sms as
GIFT (Bsnl no.) (amount)
to 53733 or 53738
Ex:
GIFT 9443613692 50

tested in west bengal and it works in other states.