Refund after cancellation not being processed by the builder

Builder has not returned the adv amount after canceling of flat. As per the contract, he should reimburse the amount after deducting cancelation fee. But no action has been taken. I ve been following up through emails, telephone and personal visit. Each time they tell we are processing the case. It has come to my notice that the case has not reached to higher auth in the office. Also, no contact information of managerial level is being provided. The canceled flat was booked and sold in 1 month that time.. Kindly advice. ....