Samiah International Builders — not given possession of flat in gulmohar estate, pending since oct 2011, paid full amount to samiah international builders

We had invested in samiah international builder's project, gulmohar estate, phase-1 rudrapur, uttarakhand.
We had paid full amount to the samiah international builders on-time in may 2011. Possession of the flat was to be given in oct 2011. Till date i. E. July 2019, no one from samiah international builders is responding to our calls or responding to emails or responding to letters we are writing to them with a request to refund the amount.