Xrbia Ambience Realty LLP - Compensation not given as per agreement for not giving possession of flat within time

Refer my booked flat at A*, at Talegaon, Ambi site. As per registration agreement, builder is liable to refund the money paid to them at an interest of *% per annum if they fail to give possession within ** months of registration. Registration date **.**.****. They failed to give me the possession till **.**. **** (after ** months)

After that, I am trying to contact them for proper compensation. They offered me a compensation of **** per month till possession, but I disagree with it. The interest accrued against my payment is much higher. I do not want to cancel the registration right now, but I need the compensation as per the interest (*% per annum) accrued for the months from Jan ** to till possession against my payment made to them. Otherwise, I would like to cancel the registration and they have to refund me the whole amount +taxes as per the agreement with an interest of *% per annum.
I am calling them frequently and sent several emails. The management is inaccessible and not answering my emails. The juniors pick up the phone calls but do not give a proper answer and do not forward it to senior management.