Ex company harrasment on dues in full and final settlement

Hi, I have resigned the company on 5th July 2023 submitted all the properties blongs to me with NOC , but in full and final settlement company dectucted an amount without any specific reason and also they deducted my last quarter incentive which i was earned in last quarter credited in my bank A/C , made dues in minus on me now they are force fully asking to return the amount , sent me a notice also . What should i do about this legal notice sent bia mail through their third party advocat ?