You are facilitating Sales for overseas suppliers for commission .it means you are acting as an intermediary .
As per sec 2(13) of IGST ACT 2017 “intermediary” means a broker, an agent or any other person, by whatever
name called, who arranges or facilitates the supply of goods or services or both, or securities, between two or more persons, but does not include a person who supplies such goods or services or both or securities on his own account;
Now as per sec 13 (8) of the IGST Act 2017, Place of supply for the intermediary services shall be the location of the supplier i.e in your case in India.
Location of supplier of service : India
Place of supply of service : India
So even if the recepient of the services are outside India still it will not be treated as export of services as all the conditions for export of services are not fulfilled ( Place of supply - India; Refer Sec 2(6) clause iii of IGST Act 2017 ) and hence taxed in india .
GST Rate applicable will be 18%
Regards,