Broker sold the land to another party without clearing dues with original owner

My father did a 'ekrarnama' with his close friend (also a land broker) on a 500 rupees stamp paper. Since they were very close friends my father did not read the 'ekrarnama' and blindly trusted and signed it. In the ekrarnama it is clearly mentioned that his friend has given my father some X amount of money as advance (which he did not pay to my father and said will give later) and rest of the money will be paid to my father when the broker sells the land and gets money. In the ekrarnama : 1. There is no clause of cancellation of agreement 2. My father's friend has full right to whatever he wishes in the land 3. My father cannot deny registry 4. My father will be responsible for any disputes But my father's friend made ekrarnama with other people but did not pay a single rupee to my father. When my father approached him for money he kept on delaying, this lead to verbal quarrel. Now my father dont want the money and wants to cancel the agreement (also sent lawyer's notice for cancellation but his friends lawyer replied back that it cannot be cancelled). Please let me know how can we cancel the agreement and solve the issue.