Gst on maintenance charges

I have purchased a flat in Khativali Village of Shahapur Taluka in Thane District and got possession in 2013. As per agreement for sale I was liable to pay maintenance charges @ 1686/- per month for three years from the date of possession of the flat. Even after three years the builder continued the maintenance charges on the pretext that the Co-operative Housing Society would be formed when the construction of adjacent building would be completed. The structure of the said adjacent building is left unattended for more than three years and the builder did not allow the flat owners to form Co-operative Housing Society. Now, maintenance charges are increased to Rs. 2248/- per month. As per my knowledge the maintenance charges is a sum total of Annual Repairs (could be 75% of construction cost of a new building/flat) and re-reimbursement of other expenses incurred on behalf of the flat owners by the builder. I have demanded from the builder to justify maintenance charges @ Rs. 1686 / 2248 per month for which he has kept silent, but informed me to make an Association and takeover the maintenance of the building vide letter dated [deleted]. The Co-operative Housing Society would have been formed within a reasonable period as per existing rules, regulations and practices if the builder had not denied to form it. In the present scenario, my question is about payment of GST by flat owners on the re-reimbursable charges, like Panchayat Tax, N.A. Tax, Electricity charges of common area, etc. and unjustified maintenance charges @ Rs.1686/Rs.2248 per month. In view of the above and I am forced to keep paying unjustified maintenance charges to the builder, I request you to kindly clarify the above points in light of the existing rules, regulations and practices in the matter relating to maintenance charges.