Dear Mr. Nageswara ji,
To substantiate Sh. Kasturi ji views, please refer to below provisions in GST Act. Department should have sanctioned you refund of CENVAT in Cash citing reference to Transitional provisions as has been done in most of the GST jurisdictions.
You should file Appeal against Order-in-Original to Commissioner (Appeal) and refund shall be sanctioned to you in Cash. At present, Order-in-Original can be challenged or else time for filing Appeal will lapse. Rebate sanctioning authority will not review his order.
Sec 142(3) Every claim for refund filed by any person before, on or after the appointed day, for refund of any amount of CENVAT credit, duty, tax, interest or any other amount paid under the existing law, shall be disposed of in accordance with the provisions of existing law and any amount eventually accruing to him shall be paid in cash, notwithstanding anything to the contrary contained under the provisions of existing law other than the provisions of sub-section (2) of section 11B of the Central Excise Act, 1944.
Sec 142(6) (a)every proceeding of appeal, review or reference relating to a claim for CENVAT credit initiated whether before, on or after the appointed day under the existing law shall be disposed of in accordance with the provisions of existing law, and any amount of credit found to be admissible to the claimant shall be refunded to him in cash, notwithstanding anything to the contrary contained under the provisions of existing law other than the provisions of sub-section (2) of section 11B of the Central Excise Act, 1944 and the amount rejected, if any, shall not be admissible as input tax credit under this Act: