Godrej Properties — godrej city panvel

Address: Adukia Road Kandivali West, Mumbai City, Maharashtra, 400067

At the time of property purchase in nov 2017, godrej sales team had promised that any changes in gst which would benefit the customers would be passed on to the customer and if i was to decide on purchase of the property on the spot, the flat would be available at a discounted price. Discount was equivalent to 50% of gst.
Now, govt. Has reduced gst on under-construction properties to 5% from earlier 12%. However, godrej continues to levy gst @12% and is refusing refund of gst amount levied in last 2 years. They are stating that discount given covers for it and i would have claimed input tax credit on gst amount. This is quite pathetic from a brand of godrej's repute: (I) discount given for equivalent to gst amount for spot booking. But gst has been charged at 12% all throughout; (Ii) how can an individual claim input tax credit.
These are some naive reasons to not go through the rigmarole of recovering the already paid gst and burdening the buyers with it.

Need refund of excess gst paid in last 2 years.