HDFC Bank — incorrect credit card practices

I have a credit card ending with 4387 and my concern is with the way i have been billed / poor customer service:

I did not receive statement for last 2 months – obviously customer care is not available. So there is a delay in payment of 12000 rupees by few days. Bank has charged me as interest / a great 9000 plus gst as the bank has a process to charge interest on payments which are not due.