Earth Towne project

Q: I have a flat booked in Earth Towne. I have paid 30% + Service Tax in CLP. I understand there was some complications in the past, due to which there is delay is construction/possesion and bank/financial cos. were not ready to fund until recently where only couple of them are coming up to fund this project. Now even after paying 30% + ST and working to get the remaining amount disbursed by funding company, I am being charged interest rate which I have no clue and was never communicated until I called them. Moreover I came to know from media about the 'zero peiod' where old customers should not be charged with interest. Please help me to sort this matter as I am not in a position to pay such high interest which makes no sense.