Sir,
According to Section 2 (6) if IGST Act, 2017 “export of services” means the supply of any service when,––
(i) the supplier of service is located in India;
(ii) the recipient of service is located outside India;
(iii) the place of supply of service is outside India;
(iv) the payment for such service has been received by the supplier of service in convertible foreign exchange; and
(v) the supplier of service and the recipient of service are not merely establishments of a distinct person in accordance with Explanation 1 in section 8.
Explanation 1 of Section 8 of IGST Act, 2017 stipulates that-
For the purposes of this Act, where a person has,––
(i) an establishment in India and any other establishment outside India;
(ii) an establishment in a State or Union territory and any other establishment outside that State or Union territory; or
(iii) an establishment in a State or Union territory and any other establishment being a business vertical registered within that State or Union territory,
then such establishments shall be treated as establishments of distinct persons.
In my opinion conditions (i) to (iv) of Section 2 (6) of IGST Act, 2017 are satisfied and hence what you are doing is export of service and according to Section 16 (1) of IGST Act, 2017 is "zero rated" supply. hence you need not pay any gst.