Builder sending demand letter without having authority NOC

Hi, I have purchased a plot in Gaur Yamuna city, greater noida(250 acres township), they have 2(2nd parkview, 32 parkview) project inside the township for plots only, rest are apartments and commercial area in it. Around 2 months ago I applied for loan through SBI, and I come to know from SBI agent that they are not providing authority NOC to SBI, so my loan cannot be approved. When I enquired the same from Gaursons they told me they don't have authority NOC for plots till now and advice me to take loan from Indiabulls and infoline agencies as these agencies are providing loan on this project without authority approvals. when I asked them why they don't have NOC even after 8 months of project launch they were saying that sir this is government work it takes time we have to provide huge money to get it approved, everything if ok from builder side soon in coming future we will get the NOC from authority, but unable to tell me confirmed time frame. Now they have send demand letter for next 30% amount which is close to 12 lakhs, I have already given them 20% amount. They are forcing us to take loan from private agencies at higher rates as compared to govt banks. When I asked them that since you don't have NOC even suppose I take loan from Indiabulls etc and later if you don't get approval from authority in that case after possession(planned in june 2018) how I will get my plot registered..? as this project is not approved by authority, on this question that gaur representative was answer less .. My query is this, since builder is not having authority NOC.. can they still send demand letter for project work..? I have taken this plot in construction link plan.