Department of Posts, India - Deduction in closure amount of Postal N.S.S. account

I deposited Rs. ***** in N.S.S. account bearing A/c no.- ******* in Ghatsila P.O. on **/**/**** with an interest rate of **% p.a. I continued the account and every year sent the passbook for interest updating. Hereafter I applied for the closer of the account in July **** but the department made the settlement pending for a long time. After putting a complain they settled the matter in April **** and calculated the settlement value of Rs. ******. But for an unknown reason, they deducted a sum of Rs. ****** and paid Rs. ***** by cheque no. ****** dated **/**/****. I am confused and can't find any justification for this deduction. Hence I request you to do the needful and take necessary action.