Poonam Builders — cheated and took extra money

Address: Thane, Maharashtra

We had booked a 2 bhk flat area 490sq ft in poonam park view near yazoo park n we were told that gst is free.
The flat cost was around 40k n we didn't have enough cash to pay for other charges n so we requested to include that in agreement value so that we get that much loan from bank.
It was a mutual understanding.

Now the builder asking for more money for that same charges which we included in agreement value n have already paid through loan.

I have both the cost sheet of including n excluding the other charges.

Kindly take necessary action against them as they are cheating us.