Consumer Redressal

I am Standard Charted Bank credit card customer and in March 2013 paid the due amount on time and to my surprise in June I got the bill which came along with late payment fees and interest added. I sent mail to customer care but did not get proper and adequate response. After numerous efforts to resolve this issue, in one call I was told that this is due to non-payment of April bill which I did not receive.He told me that, Yes, there was some technical fault due to which your bill was not generated and could not be sent.I then asked him that I have no fault here so why should I be penalized for late fees and interest, then he asked me to just pay the amount I have actually spent during this period and I did the same but that day onwards I have been receiving mails and call on my mobile for payments. I want to pursue this case in the forum as this is a harassment to me and most importantly I have also been threatened for downgrading of my CIBIL rating which is a big financial loss to me