1. If as per the agreement of sale entered in to by the buyer with the seller is 3 months then you can cancel the agreement by informing the seller through written communication.
2. But, however, if there is a penalty clause of Breach of Contact, then the amount agreed with the seller has to be adhered to.
3. If there is no such clause of penalty in the agreement of sale, then you can send a legal notice to the seller for returning back to you the advance amount which you had paid to the seller.
4. If specific time for concluding the deal had not been mentioned in the agreement of sale, then the validity would be 3 years.
5.You can go the legal way by enforcing the Specific Performance of the Contract on the Seller by approaching the appropriate Courts of Justice.