I purchased underconstruction 'commercial' unit in a building and also got registered. Now builder has changed plan and started constructing residential building at same location. I am not sure how he got an approval of it. As a buyer I asked refund from the builder alongwith all charges and damages, but builder refused and offered me different flat in residential building and asks for additional amount based on today's rates, which I do not want and I refused. As amount involved runs in lacs, what should I do, this is a pure case of builder cheating buyers. Moreover he is not taking calls or replying to communication now. He do not provide written communication of change of building plan, all he does is the verbal communication about whole changed plan. He is also not bothered about this issue. What are the options available to me?