Unfinished flat purchased

We  have  booked  your  flat   on  april  2015  . and settled full amount  for that flat  .  near by two years  passed    .  still the  flat is  in    basement   stage . the  completion     period is 1 ½  years . but the flat is   in    basement  stage . meantime  builder  agreed  to pay as rent  Rs5000/-  from  dec  2016 in construction agreement   but  he is not ready to pay   the amount   . kindly  what action  should I take .