1. The claim of the nhospital has now become time barred since it has passed 3 years limitation period,
2. As such the hospital can not claim the said amount directly from you since your father has not committed any mistake and if anybody has created any mistake here then it is the hospital itself for sleeping for such a lond time and also by DGHS authorities if it is a fcatr that the said amount was trsneferred to your father's account in place of the hiospital's account,
3. Send a reply to the hospital's legal notice through your lawyer refuting the claim that the said money was transferred to your father's account,
4. Moreover, you can not be forced to pay for your father's hospital dues after his demise,
5. In case of any criminal intimidation, file a criminal case or lodge a police complaint.