what to do po if the developer refused to give refund of 50% for unit cancellation,

We cancelled po our condo unit in qc. after a month a disposition letter sent to us by developer giving us only 1/4 of what we expected of the 50%. Not amenable we replied to their email and demanding the 50% refund for all the payments. 1month after they sent another email and said that the dispositon letter is final and the management refuse to accept our request for reconsideration and given us only 2 days to reply with the email with the help of a friend a demand letter was sent but after 2 weeks they said the its final and since were not amenable they will close the request. My friend said that we should file complain at HSAC. What to do pls.