False Allegation by employer on M.B.A. Institute

Hello Sir, I am working as Mid-Level professional in MNC. I joined my company 18 months before, now during background verification process, my employer (HR Department) initially questioned on my Distance Learning M.B.A. degree. I have explained them the process of verification, post which after 2 months they are questioning about the Institute's location. I have enrolled for M.B.A. from Mumbai branch and that franchise doesn't exist any more. However, institute do operate from other locations and primarily through online mode. My organization's HR team is now questioning about the same and threatening to take a strict action against myself. In a detailed discussion, they shared that they don't have a question on my M.B.A. degree, however their background verification agency reported that Mumbai Franchise doesn't exist. Mumbai franchise is not there, however institute is properly function under Govt. Reg. No. E/2667. Please help me to share your advice what should be done now? Regards, Dipin Manani