Irctc — Train cancled but tkt amt not refunded

I had booked ticket vide PNR No[protected]for fm patna to secundrabad Sup Exp for journey on 10july Jun 2015 from patna to secundrabad boarding at patna . On 10 july at 12.25 hrs on reaching station i came to know that train is cancelled. I could not cancel my ticket thinking that if train is cancelled there will be autho refund in the accout booked on line. On enquiry after four days i got reply that amount can be refunded only on filing TDR within 72 hours. The cancellation of train is from Railway side there is no my lapse so I request to credit the amount of 8171/- in my account