2017-18 outward case - Goods and Services Tax - GST

Crux of the case: due to ignorance and being new to GST, in 2017-18, the taxpayer had inadvertently wrongly declared our outward liabilities in GSTR-1 in IGST, CGST, SGST, and vice-versa, resulting in the demand order. As per the order dated 21.12.2023, they have to pay Rs.743 223/- towards IGST. However, due to the above wrong showing in GSTR-1 , they had paid excess tax towards CGST and SGST @ 307456/- each, totaling 614913/-. Hence, fled a rectification application with a request that this point has to be reconsidered and enclose a copy of judgement dated 03.01.2024 of Hon ble Kerala High Court in support of their defense. Given undertaking to pay the differential liability, if any after adjusting the excess paid cgst and sgst. However, the rectification application was rejected and they want to go on appeal. kindly advise.