Cancelling Sales Agreement for a Land in Kolkata

I have purchased (agreed to purchase) a land in Kolkata from a builder. We did an agreement where he has mentioned that he will do the plotting and develop necessary facilities line road and electricity to the given area. And when the development is done, we will do the final sale agreement. Till then we had to pay the agreed amount on yearly and % basis. However, now we don’t see any development from the builder on the given area, so we wish to cancel the agreement and take back already paid money. This clause was mentioned in the agreement as well; the clause says that we can cancel the deal any point of time and we shall get our money back with some % deducted from the paid money. We tried calling and sending notices to the builder, but we are not getting any reply from him. We visited his office as well but he doesn’t seems to be available most of the time. Every time he makes a fake promise of giving money back. My question is what we need to do in order to get out money back from him. What legal procedure we should follow.