NOC not obtained hence buyers name will not be endorsed on share certificate.

I sold the flat in coop housing society in december 2019. Buyer was introduced by chairman of the society and okayed. He gave format for taking signature from the residents of block which was duly completed as no one had any objection. Further an affidavit duly notarized was asked for by the chairman and was duly completed and submitted. No dues certificate was also given. November 2019 we were told that committee will call both parties for meeting one to one for which we were not called as the committee did not meet. Sale deed was executed on 19/12/2019. A request was submitted on 22/02/2020 for giving NOC to which no response from chairman. They are verbally asking for Rs. 30000/- as penalty plus 18% interest for endorsing buyers name on share certificate. My question ; 1 Is it binding on me to have the NOC from society chairman 2 Can committee decide in the meeting to ask verbally for Rs.30000/- + 18% interest 3.Can they refuse to endorse the buyers name on share certificate and keep my name as owner of the flat and demand yearly maintenance from me. Kindly advise. Thanking you