Refund - Credit note for export of services issued with IGST - Goods and Services Tax - GST

Dear Experts, We are providing recruitment outsourcing services to our clients located outside India and its fulfilling otherwise all the criteria of export of services as envisaged under 2(6) of IGST Act, 2017 . For one transaction we have issued Commercial invoice to the client located in USA and based on tax invoice in INR currency paid IGST . At the time of Filing GSTR-1 the same has been reported as Export of services with payment of IGST and in 3B also the same is reported as zero rated supply. Later, Credit note for the said commercial invoice has been issued to the Client and accordingly credit note in INR with IGST also issued. Now, we have paid IGST at the time of issuance of tax invoice however refund is not claimed as amount is not received and now credit note has been issued. So, the question is whether refund can be claimed of IGST paid at the time of export invoice ? If yes, under which category?