Gst liability of landowners in jda

Request to please provide reply to my email on the below request. We have entered into Joint Development Agreement (JDA) in Sept '16 and Supplementary Agreement in April '17 with the details of identified flats with Builder with 50%-50% ratio and the possession of flat will be given to us by end of May 2018. Builder is now insisting us to pay GST on our self occupied flats. I need your guidance on how to deal with this scenario. The two flats received by us are for our self possession and there is no sale transaction involved. We have given the plot for development to avail the services of Builder and we have also given share of our land towards availing the Builder services. We have already lost 50% of our land share to Builder and again why should we be paying GST for these services of Builder. We were told by few Chartered Accountants that we need not pay any GST for self Occupied Flats in JDA as there is no sale transaction involved. However, need your final inputs on GST. Awaiting your expert advice. Appreciate and Thanks in advance.