All amenities not provided & cc not obtained by the builder

Me and my husband bought a 2 BHK flat in a complex comprising of four buildings which has been duly registered. The builder has taken full consideration amount at the time of registration. However, the project is not complete as per the clauses of the agreement and all the amenities and facilities have not been provided as per the agreement of sale. At the time of sale the builder has taken 1 year maintenance amount from all the buyers and it was mentioned in the agreement that on handing over the project after completion the society formed by the flat owners shall maintain the same. However, since the project is not completed till date and CC has not been obtained by the builder, it was maintained by the builder and the flat owners used to pay the maintenance to him. In the month of May'17 the fat owners served a notice to the builder thereby gave one month time to complete the remaining work of the project and obtain the CC but the builder paid no heed to that and threatened us that he will stop the maintenance service. At this juncture, the builder suddenly without any proper/official notice wants to outsource the maintenance service to a third party from 1st July, 2017. what are the remedies available to the flat owners.