Builder imposing late payment fees Interest and Rera is helpless

I booked a property 3 years back with 5% download payments & 90% loan from bank and rest needed to pay at the time of possesion and possession date was of october 2018, but on feb 2019 i received a letter from builder that asking for remaining payments and interest with late charges and unjustified maintainance changes for releasing possesion. I had conversation with builder to remove all kind of penulty and late charges but builder is not listing anything. Even builder doesn´t have RERA certificate nor OCC. In this case how builder can ask final payment with any clearance. So i filed the case against the builder in RERA in month of feb 2019. Now i got order from RERA, but order seems in the favor of builder. Now i am not getting what should i do now. Amit kumar