Consumer Redressal

Hi I had booked flat from Skyline constructions Bangalore in 2006-07, agreement was signed for 33 lakhs and promised completion of 3 years from that date. They have not registered till date. When i ask them to register the flat on to my flat, they are asking for PDC (post date cheque) and they would return the cheque against DD on the date of registration. I have already paid 30 lakhs to them. Now they have increased the cost and moved the price to 42 lakhs, they are charing interest and they have unattended work in my flat. They have harrassed mentally not sure what to do. They are taking advantage of my position. Please suggest how to approach on this. Thanks & Regards Sridhar