What is the procedure for withdrawing NSC on maturity after changing city?

I bought NSC for tax saving purposes several years back in Kolkata. Presently I am in Chennai and my certificates are due for maturity. However when I visited the local post office, they just scared me away. I am told that they will send the certificates by post to Kolkata and if I am lucky they will get confirmation in about 3 months time. After that, I have to apply for change of address and give address proof. A representative from local PO will visit my house to confirm if I actually stay there.

They will issue me a cheque only after all these formalities. Does anyone know an easier way out?

First of all I am not very sure if the loan taken ANY fixed deposit is a secured loan.?

Secondly, I also want to know if, I take a loan against a fixed deposit and I am not able to repay it, at the maturity date, I shall have a liability towards bank.
As far as basic logic says, bank did not lend any money to me and what I have is a part of my deposit.Why should bank ask for more money from me then?

Any pointer links to Reserve bank of India with norms for these conditions shall be helpful.