[Resolved]  HDFC Bank — dispute of money

I am a account/credit card holder of HDFC bank. my card no. is [protected]
To pay my credit card amont, i have got settlement letter from bank (ref;no.: S[protected] according to which Rs 4000/- monthly installment has been decided. i had paid regularly till feb '09 and for which i have all my receipt with me. but in march i had only paid Rs 1400/-. now, on against 1600/- Rs left bank has deducted Rs 23,808/- from my bank account. I had loged a complaint in HDFC bank also but i have got a negative response.
I am unable to understand the amount of interest rate that the bank is leveling on me. if bank is taking interest on the whole amount that i had initially, then what about my money that i had paid till now.