GST on repair of Jewellery by Jeweller - Goods and Services Tax - GST

Dear Experts, A jeweler is providing services of repair of jewellery to end customers. It is outsourcing this work to job workers who charge it GST at 5%. Further, the jeweler is also invoicing these services to customers at 5%. Department has now raised issue that tax on these services was 18% as per Entry no. 26(iv) of NN 11/2017-CT(Rate) as 5% applies only to job work which only covers services provided by registered person to registered persons as per definition under Section 2 of CGST Act 2017. Kindly advice correct course of action in this regard.