Refund of advance payment

Sir- In the month of April 2020, I paid an advance of 1 lac rupees through online offer price to one of the renowned builder. They have mentioned in the advertisement that 100% refund, if we cancel the booking on or before 31st May 2020. I spoke to the sales guys on 15th May 2020 and informed that I m cancelling my booking and want a refund. On a safer note, I sent a mail to them on the same on 30th May 2020. Till now, they have not given the money. I have called them multiple times and sent more than 20 mails. A month back I got a mail from Customer Relations team that my booking is cancelled as per the terms I will not get back the amount and it is forfeited!!! When contacted the sales guys they inform that I will get back the amount, but they refuse to give it in mail. Please advise how to get my hard earned money back. Thank You.