The petitioner may complete the formalities and remove the deficiencies, if any, seeking refund of G.S.T. within fifteen days, whereupon, if it is otherwise permissible under law and there is no legal impediment in this regard, the opposite parties shall proceed to consider the claim of the petitioner for refund and take a decision thereon within six weeks. Petitioner may claim interest also, if otherwise permissible and a decision be taken in this regard also. Thereafter, if the petitioner is aggrieved, he can invoke the arbitration clause or seek other remedies as may be permissible in law.