Advance maintenance charges by builder

Dear sir / mam This is regarding my flat in virar which I bought in jan 2019 in fully constructed building. I had done the registration in feb 2019. The possession date was in June 2019. After the registration I came to know that the building has got 95% completion certificate from architect certificate and remaining 5% will be obtained within a month. I was in need of immediate possession of flat as my rental agreement of my current flat was over. I informed this concern to my builder and he gave me the optionn of soft possesion of flat in March 2019 as legal possession was not possible due non availablity of 100% complete certificate and O. C. Before soft possession I paid advance maintenance of 18 months @ 3315 rs p.m and 1000 rs p.m electricity charges for 1 year. Since the time of soft possesion in March 2019 we had lots of issues on terms of electricity fluctuations and security issues, water leakage, 100% architect certificate, O. C etc. The builder had till date not solved the above issues. Now in June 2020 he had given us a notice of additional maintenance demand of 1 year as he is saying that the advance maintenance has been exhausted and he is paying out of his pocket. Now my question is is the builder legally correct in terms of demanding additional maintenance even if I have paid him 18 months advance which is not completed yet. What are my legal rights in this matter if builder keeps presurring me and disconnect the water and other services. Please help 🙏