Recovery from defaulted builder

1. I had entered into an agreement with m/s Keshari Builders Pvt.Ltd., Bhubaneswar on 31.03.2008 for construction and handing over of a triplex havign land area of 2000 sq. ft and built up area of 2300 sq ft at a consideration amount of Rs.19.5 lakh. 2. The consideration amount of Rs. 19.5 has been paid at one go on 31.03.2008 to the builder. 3. As per the above agreement, the builder has to pay double of this amount ,if the construction and handing over of the property could not be completed within three years from the date of agreement. 4. After lot of persuation, On 13.09.13 , the builder has issued a provisional allotment letter, stating that flat no A4 has been allotted to me and that the flat shall be handed over to me within 18 months i,e 12.05.15.However,the land area has been reduced to 1600 sq ft from 2000 sq ft. 5. I used to call the builder no. of times in between to finish the job at the earliest, but in vain. 6. The builder agreed to complete the sale deed of the proposed land and it was done on 13.01.2015. 7. Presently,I have lost all my hope for completion of the project and do not want to be swayed away by the false promises of the bulider and now we are unable to contact him as most of the time either he is not in the office nor he picks up any phone call. 8. Iam passing through a terrible mental agony and feel duped/harassed by the builder since I have invested ny hard earned money taking loan from PF account. 9. Now I dont want the flat any more and I want my money back with applicable interest. 10. Please suggest a suitable method/mechanism to fight against the builder.