Likely Fraud Bank Recovery Agents

My father is aged 67 and is bed ridden. He is receiving calls from some people who claim to be from ICIC bank stating that he has a credit card due from 2008. We have not received any outstanding letter on an ICICI letter head neither had anybody visiting our house in this matter. Moreover, when we asked them to send the details, they said they would charge for the transportation cost of the man who will bring it. Now they also have started calling regularly even abusing on phone and threatening to file a court case. I have called for a CIBIL report of my father which is awaited. In the meanwhile, What should be done?