Bengal Shelter Housing Limited - Flat not delivered

I paid the initial instalment for a flat in the `Neel Diganta' project of Bengal Shelter Housing Development Limited, which came to approximately *,***** rupees, including allotment money of Rs *,*****, application money of Rs **,*** and service tax of Rs **,***. They were supposed to handover the flat within ** months from the date of allotment, which is **th April, **** and according to the progress made in the construction we were supposed to pay the remaining money in six instalments. It is also mentioned in the allotment letter that if they fail to deliver the flats on time, then would pay interest at the rate of a savings account in a nationalized bank. But after they took the initial instalment they did not start work on the project and upto ****, they kept on promising that they will start their project within ** days. and requested us to be patient. But sometime after that after repeated calls, Ms Sujata Saha informed me some time in **** I think that the project is stalled and that I could ask for refund. Unfortunately even after repeated requests I could retrieve only approximately * lakhs of the money I gave, leave alone the interest, and that too asking money from them I feel like a beggar. This whole experience has been extremely distressing for me.