Casagrand — PMAY Concessional GST denied by builder

Address:	Casagrand Builder Private Limited New No.111, Old No.59, NPL Devi, LB Road, Thiruvanmiyur Chennai – 600 041, Tamil Nadu, India
Website:	www.casagrand.co.in

HI,
i have booked an under construction apartment with casagrand builders(https://www.casagrand.co.in/) on Apr2019 with 12% GST. They have constructed a skeleton of my block like pillar and roof and acquired 82.5% of total cost with in Jan2020.
But other blocks has no steady progress, i put a hold one stage payment.
Meanwhile i applied the PMAY and got subsidy into my home loan account on May 2020.
In this year only they resumed nearing the completion.
The project supposed to be completed in June2021. More than 1.5 yrs they are delaying and still putting delay charges for my pending amount and saying will be collected at the time of handover. For now, i have paid total of 92%.

Now, when proceeding the registration, i came to know that, under PMAY we get 4% concession in the GST. When i check the same with them, they deny this feature as i should have informed this earlier and they already filed the GST. But based on government notification F.No. 354/52/2018-TRU dated 7th May, 2018, its their responsibility to provide the govenment benefit to the buyers. i also stated this to them but still they are refusing to reduce the GST and adjust the excess with handover payment.