Punjab National Bank [PNB] — loss of money through net banking and non response from the bank on the issue

I have been associated with punjab national bank for quite a long time.in july 2017, an amount totalling to rs 50, 000 was lost from 3 accounts maintained with angamaly branch of punjab national bank, ernakulam, kerala. The same was reported to the branch in support of the circular of rbi dated rbi/2017-18/15. However no response has been received from the bank till now. We are legally eligible for refund of the lost amount. However the same has been delayed due to non response from bank officials. A period of 4 months have elapsed from the date of said event. Kindly consider the same.