Cheque bounce because allahabad bank merged with indian bank

I had received 3 PDC cheques(dated 15Jan,2022) of Allahabad Bank in lieu of interest free loan given to borrower in month of July,2021.In respect of which we had done proper legal agreement, signed by borrower( contains clause-said cheques no., default can attract criminal offence, interest free loan etc.). But the problem is that when we had deposited cheques in 23 Feb,2022. It was bounce due to false cheques, false arise due to his Allahabad bank merged with Indian bank and officially it was announced that allahabad bank cheques will become unusable after 1Oct,2021. That I comes to know today after cheque being returned to us by bank. How can I proceed in this case? I had cheques returned by bank, hard copy of legal agreement signed by them containing said clause that cheques was issued for payment of Interest free loan given to him.