Is NOC required for SRA bldg with no society?

I have SRA flat in jogeshwari area of Mumbai.. flat was purchased directly in 2002 from builder. This building has no OC and also there is no registered society.. however, the residents have formed a group and they call it society, they hold meetings, ask for maintenance which I am regularly paying. I don't live there, I have never lived there infact.. the flat was occupied by my late father who stayed there till his demise in 2011. I pay the maintenance since 2014. However, these people had given me a bill of 59000 in 2014 and something claiming it to be maintenance for the past years and on questioning, they say that they used to collect maintenance before also, but since my father lived alone and was an old man, they didn't bother him for that.. I have simply refused to pay any previous charges , however, I religiously pay maintenance of 800 since it is introduced later in a meeting I attended in 2014. Now my only question is it's a SRA flat with no oc since the builder has stopped taking interest in the bldg, society is also not registered.. now I want to sell it off but I am sure that these people won't give me an NOC.. so is it really reqd to have an NOC from them??