Cancellation of flat after the agreement

Hi sir, I would like to clarify the below below doubt.I have booked the flat with the builder in Bangalore. When i plan to book the flat with the bulider with 2 lk ruppes booking amount.(180,000 - for booking amount / 20000- for some fund (no receipt given).They pushed to sign the agreement on the same day and collected 6700 rs for e stamping and asked to me to give cheque for 10,00,000 rs post dated cheque. I have give 3 cheques( 20k - fund amount,1.8lks- booking amount,10 lk - part payment.) But some i got to know these ppl dont have proper document and i have sent message to that builder guy to stop executing the agreement and i asked all documents to be verified. But noone turned up. Now i have asked to cancel the flat. now they are hestitating to do that. One good thing is i have cancelled two cheques (1.8 lks & 10 lks) , but they took the fund amount of 20k from my account. Now i dont have the agreement (green sheet) which i have signed. Note: i have signed only in green sheet not on the e-stamped paper. my question: 1. I have signed the green sheet. it will cause problem for me?? will it be considered as the agreement.? 2. Do i have to pay any cancellation charges. no where it was mentioned in the booking form. But im worried about the agreement(green sheet) which i have signed? 3. can they execute the agreement without getting that 12 lks ? Kindly help on the above .