Sir,
According to para 3.2 of CBIC circular No. 88/07/2019-GST dated 01.02.2019, “there is no restriction on invoicing of export contracts in Indian Rupees in terms of the Rules, Regulations, Notifications and Directions framed under the Foreign Exchange Management Act, 1999. Further, in terms of Para 2.52 of the Foreign Trade Policy (2015-2020), all export contracts and invoices shall be denominated either in freely convertible currency or Indian rupees but export proceeds shall be realized in freely convertible currency. However, export proceeds against specific exports may also be realized in rupees, provided it is through a freely convertible Vostro account of a non-resident bank situated in any country other than a member country of Asian Clearing Union (ACU) or Nepal or Bhutan”. Further, attention is invited to the amendment to section 2(6) of the IGST Act, 2017 which allows realization of export proceeds of services in INR, wherever allowed by the RBI.
Therefore, even when you receive the payment in Indian rupee you can claim ITC refund subject to approval given by RBI.