Legal procedure to recover advance money from builder

I have Booked a flat in 2015 and for the same I paid booking amount of 54000/- and builder had agreed to start the construction in August 2015 but there is no activity and when i asked builder about this and the representative told me that they haven't got any updates on the land and the permission are not still not received from the concern department, after that builder send me demand letter to paid 19% of the agreement value and also mentioned in Allotment letter that if I failed to pay then they will charge me 21% interest per annum, so i paid the same but even after that no response from builder. after several visits to the builder office i haven't got a proper answer. in last visit i come to know that they had changed the layout and the number of floors and also the amenities in the project, so i asked builder to cancel my allotment and refund the amount for which builder agreed but its been 2 months and i haven't received my refund. what next step to get my hardearned money.