Seeking Refund of deposit due to personal reasons

Dear Sirs, In June 2023, I deposited Rs 4.3 lakhs as 10% of the total value with a builder for a property in an upcoming mall in Noida. The payment was made through cheques. The builder representative took copies of my essential documents as formalities and made me sign on the agreement. Though nothing was delivered to me as the representative conveyed that the document needs to be filled by the staff and would be delivered later on. In September 2023 I made another deposit of Rs 1.5 lakh. Thereafter due to some personal reasons, I decided not to go ahead with the property though builder kept reminding me of due installments while even softly threatening me forfeiture of deposited amount if I do not pay the balance installments. In May 2024, I met the representative at his office and he told me that due to non-payment of dues, my allotted property was cancelled and given to someone else. He even told me that as per the agreement, the chargeable interest rate is very high and my deposit cannot be refunded now. He however offered me another property in the same construction and provided me with a new payment plan written on a plain paper and then stamping/signing it. I anyway did not go ahead with the new plan. I want to get my deposited amount of close to 5.8 lakhs back. What would be the necessary steps? and whether is this possible at all? Any suggestion would be helpful. Yours sincerely R