I received a cheque bounce notice from a friend. What to do ?

Hi, from ahmedabad, had a partnership firm established in rajkot with an accquaintance as a partner. the business was in operation from 09/2015 to 05/16 post which it was mutualy agreed to discontinue the partnership. the legal procedures of dissolving the partnership were not done and the bank accounts were not closed as a large amount of TDS deducted was to be claimed. Have recently recieved a notice from my partner claiming that i had committed an "X" amount due to him from the proceeds of the business and that the cheque that I had issued has been returned by the bank due to insufficient funds and that i am requested to pay the dues to him along with the legal cost. please advice the procedure after receipt of such a notice. The amount mentioned in the notice is absolutely atrocious and almost " Laughable" as such amount of money was never earned by the firm during its operation. This can be easily proved from the firms bank statements. Please advise.