State Bank Of India - Credit card fraud

I had received a message on my phone on *th Oct, ** regarding the transaction of Rs*****.** around *-*pm. I immediately called the bank to block the card as I have not used my card for any online transaction. It took an hour to block the card as I was on hold for long. Then I get I communication from the bank on **th December,** saying that they have received a communication from the merchant saying that the customer used the card online. I wrote back to the bank saying I never used my card online for the transaction of Rs*****.**, it is a fraudulent charge. Then I get my statement showing the charge and the bank is asking me to pay, so I had an argument with the bank and asked them to reinvestigate as the reason they gave me is that they never received an email from me regarding this fraudulent charges when they contacted me through email to inquire about the change in ** December, **. I showed them the proof that I did send an email to them from Chauhan.durga@yahoo.in, then they say that in the record they have my email address as chauhan.durga@yahoo.co.in. I told them that it's the same email address so they reopened the case in January,**. When I called them today on *st Feb saying that the payment is due on **th Feb so what should I do. Then the bank says that I case was never reopened and the investigation shows that the customer used the card online. Please help me as I didn't use the card for the transaction of Rs*****.**. The bank is not ready to help. They don't even know what is happening. Please find attached the dispute form I filled with the bank and my statement showing the fraudulent charge.