NOC for Transfer of flat in Coop Housing Society, Kolkata

Property is a Flat in a registered Cooperative Housing Society in Kolkata. The land on which the Housing Society is situated was obtained on long term lease for 99 years from the Board of Trustees for the Improvement of Calcutta, commencing from 2nd day of September, 1977 with option for renewal for a further period of 99 years. My late father was an original allotee of the flat. After his demise I being his son and registered nominee of my father in the records of the society, became the sole member of the society and absolute owner / sub-lessee of the said Flat in the society and accordingly share certificate allotted to father was also transferred in my name. The flat has also been muted in my name in the records of the Kolkata Municipal Corporation. I have now found a suitable buyer for the flat and based on my application, the Cooperative Housing Society has issued a NOC for the proposed transfer. The buyer has approached a Bank (SBI) for obtaining a housing loan. But the Bank is demanding to know under what Power the Cooperative Housing Society is authorised to issue the NOC for transfer. According to the Bank the NOC should rightfully be obtained from the Lessor, unless that power has been specifically delegated to the Society. Rule 138(1) of the West Bengal Cooperative Societies Rules, 2011 under the West Bengal Cooperative Societies Act, 2006 is very clear: "In all cases of transfer and letting out of land, house or apartment written consent of the society shall be required." This has been cited to the Bank, but they are still insisting on NOC from the Lessor. How to tackle this situation?