Refund of advance given to builder

Hi sir, I booked a flat in noida last year and gave advance money as down payment and then as instalment of 5 lambs via chk & DD. I got the BBA to sign and submit back to builder but due to some of the unacceptable condition I wrote back to them and asked to change the BBA. They did reply by mentioning that the format is fixed by the company and they are not authorized to alter it. They can give it only their own letterhead. I hold the Agreement and did not sign it , neiher gave any further instalment to them. Now they are pushing me to pay a Sum of approx 26 lakhs as per agreement, which I did not singed till date. Am I liable to pay them ? Further, the progress of project and the response of the company, both are bad and I want my money back. What should I do, the current situation is that,they don't want to refund my money and I did not singed the Agreement till date. The agreement is still under my possession in unsigned form...... Please suggest me ways to get refund ASAP. Regards Ankit Akhilesh 8743890898