Forcefully signed 3 cheques after giving full payment

One of my friend given 12 lakhs for about 9 months just on phone and through internet banking and not any signed documents and on phone i m agreed to give 2-10% whatever amount i get in share market. I have returned 15.75lakhs near 3-3.5% interest. now he told to give 7 lakh more of approx. 10%. he called locale police on 112 no and said that i am not returning 7 lakhs. The police told and signed through me on blank paper that i give start some money after 15th nov 22 and take 3 post dated cheque of march 23, jan 24 & nov 24 of 7lks total and he accepted that given in written with signed that now there is no problem. he come to near my house and said that if u refuse i will be shouting that u are not refunding my money. What should i do? this case is of 12th aug 7pm night Presently i have stop the cheque from bank only. Should i have to complain online or near police station to said he take forcefully signed cheque and there is no such proof that i given in written that i will give 10% interest. All amount debit and credit is available in netbaking. Please suggest what to do