(4)Every contract between an insurer carrying on life insurance business and a special agent, or between a chief agent of such insurer and a special agent, shall be in writing and the terms contained in Part C of the Sixth Schedule shall be deemed to be incorporated in, and form part of, every such contract:Provided that the Authority may, in the case of a contract between a co-operative life insurance society as defined in clause (b) of sub-section (1) of section 95 and a co-operative society registered under the Indian Co-operative Societies Act, 1912 ( 2 of 1912 ), or under any other law for the time being in force and acting as a special agent, alter, to such extent as he thinks fit, all or any of the said terms.