Summary suit case against legal heir

Yes they can file a summary suit against you, but if you have paid already 70% then appear in court seek permission to deffend your case and get endorced in court that you paid already 70%, and make installments for rest of unpaid amount

They may not file a separate case, but they implead you as legal heir within a reasonable time and it all depends on such legally valid documents, as banks consider signed by you as an acknowledgment of debt, and the limitation period starts from that date of last credit challan signed by you.  Care more about CIBIL rating and if you can afford to pay it back, do it through one-time settlement.  The details provided are not sufficient to give any precise guidance.  The purpose of the loan, how it was utilized, who is enjoying or taken over such business etc are important factors to be considered.  The word "hearing" may not have been properly used, and it may be an expartee decree or decree against your father (not in favour of your father).

Legal heirs are responsible to clear the debts especially bank debts. Inheritance is the practice of transferring property, titles, debts, rights, and obligations to the legal heir of a person upon the death of that person either by way of ‘Will’ or through the prevalent laws of succession. 

You are liable for the debts incurred by your father to the extent of property inherited from him.

The Bank do not file summary suit but other type of suit for recovery against all legal representatives of deceased borrower, depending upon outstanding amount vis-a-vis pecuniary jurisdiction.