ICICI BANK- Harrasment after 14 years after recovering of security

Need help, please. My father had paid off his 6 months EMI in 2005 withICICI back in Oct/Nov 2005 by cash. (Remaining balance was approximately Rs.120000 to 150000) he did not have a chequebook handy so he paid cash as the ICICI representative gave him a receipt. Due to some personal issues, he was unable to pay two months EMI for Rs. 6000 for the personal loan, so ICICI bank collection representative misbehave with him and snatched his car which was the issue by the standard chartered bank by a car loan, those people told him that his car loan has been transferred to ICICI bank from standard chartered and due to your two month personal loan due we are authorised to take over your car. He assumed that loans were discontinued as the bank has taken his car which was his only source of income, so he approached the ICICI bank to return the same only after then he will be able to pay an outstanding amount, ICICI bank denied and harassed him for few years by saying that let's do settlement, give us 22K or 25K and close this loan. He wasn't notified of the transferred policy of them nor he received any legal notice from them, now after 14 years, they start harassing, giving us threatening calls, visiting our residence. We have all receipts and the notice stated that we are recovering the car from the ICICI bank. 1 month ago he got such a call telling him that he is a defaulter and he owes the bank Rs.450,000 for the personal loan. A collection agent came to my house a few weeks ago for the payment. I told them that show us your identity (Aadhar Card or voter id card) but the collection agent was extremely rude and insisted that I have only a bank identity and insisted us to make a payment. When we asked why he wasn't contacted all these years the only response we get is that they are contacting him for the last 4 months so that should be good enough. We asked for proof of communication but they have refused to provide any more documents. They just gave me a statement which shows an escalated amount because of all the interest added. I got a call yesterday as well asking us to make a payment. I denied responsibility for the loan. Again I asked for proof of communication to my email address to which the agent was very rude and insisted that my father was a defaulter. I told him that I would like to write to the ICICI Consumer Office to clarify this but he said that me writing anywhere or involving a lawyer isn't going to help me. He refused to give me his ID number of his office address. Please help me. All suggestions are appreciated. Thank you.