SBI Credit Card — fraudulent transaction and non-payment by sbi

Ref: interaction id - 1-[protected]

Sbi cards reported a transaction on 01.07.17 at sarvesh jewellers gwalior on my credit card no. For rs. 18, 500/- through an sms. I was at chennai at that time. Immediately called customercare [protected] and blocked the card.
So far i had not shared card details or pin with anyone. My card was of chip card type, yet transaction was done bypassing all security features of sbi cards. How?

I had not received otp at the time of transaction.

Meanwhile they send a standard response that investigation will take 120 days and you should clear dues by due date.. So i paid that amount to avoid finance charges, late payment fee, gst, etc

After giving my mobile statement and landline internet use statement to prove that i was at chennai, sbi cards declines to accept.

I wonder then what should a customer like me supposed to do? Feeling sad and helpless..