Validity of sale agreement

You issue legal notice to the builder to perform his part of contract within a 15 days.  If he fails to do so then file a suit for specific performance of contract.  You contact your advocate he will guide you in detail about the agreement of sale and new supreme court ruling on it.

I do not wish to get into court / cases unless it's the last resort. I just wish to know if legally my agreement with him can be considered void. As per the agreement, I have paid 100% for the additional area also (again a mistake by staff of the builder). But both of us know the additional area still needs to be paid for, but as per the agreement I do not owe anything to the builder. I do not wish to be dishonest hence ready to pay for the additonal land. But the builder instead of being obliged that I am ready to pay wants me to pay at the current rate. I have taken up this issue with the Director of this(builder's) company (apparently the mistake was made by his staff). Before I talk to him, I wish to know that can I tell him I have nothing to lose since I have an agreement that says I have paid 100% for the land, but being civilised I am ready to pay for the extra land and he instead of being grateful to me is cheating me. So far I have been polite to his staff as well and they think I am needy. Can I let them know that they better charge me at the purchase rate or else I will pay nothing. Please advise. Thanks,