i want to close Indian bank saving account. will I be forced to close credit card too ?

Different banks might have different rules but in general Credit cards are not linked to any bank account. So, closing your SB account should not have any effect on your credit card provided you make alternate arrangements to pay off your bills

If not you can convert your account to zero balance account or maintain minimum balance if needed you can continue to use in future 

I had a allahabad bank account which got converted to indian bank account few years back. I tried to close the account but the  employees of these gov banks are pathetic. I withdrawed all the money from my account and the balance now shows just - . There is no amount shown just a - sign is displayed in it. So my suggestion is to close the account and shift to hdfc or icici for much better service