Maintenance security (interest free) + maintenance charges in advance for a period of 20 months appx

I have booked a flat having super area 2380 sft in Jan 2013 and agreement was signed in Feb 2013 after paying booking amount. Expected posession period was 3 years + 6 months grace period. Builders have sent me a letter this month for possession Also sent ma a letter that builders have appointed a Maintenance agency and for maintenance and I have to pay : a) IFMS -Interest free maintenance security of Rs. 71400/ = 2380* Rs 30.00 psft/ b) In addition to the above, I have to pay in advance of Rs. 1,10,000 to the Maint. Agency, at the time of possession for the period August 2018 to March 2020- 20 months. (monthly charges @ Rs. 1.98 per sq ft for 2380 sq ft super area= Rs. 4712.40 + GST) Is this demand of Rs 1,10,000/- is justified ? At the time of booking of said flat, condition was that flat owner will entered into an maintenance agreement but rates for per sq ft and there was no written statement that advance payment for 20 months is to be paid. There was indication for IFMS " Rs. 30.00 per sq ft to be paid on possessiion. Please help me in this matter and guide for further IF REQUIRED I CAN SEND YOU THE SCANNED COPY OF LETTER AND COPY OF AGREEMENT FOR MAINT. Balbir Singh Ranot [deleted]/ [deleted] email : [deleted] Flat at Ghazipur, Zirakpur- distt Mohali.