NY India embassy has this posted on their website. This one pager has general information about Aadhaar card for OCI/NRIs and the below paragraph relating to mobile connection. There is a hyper link to the "placed here" that takes you to the actual DOT communication to the service providers for verification for OCI/NRIs relating to mobile connection transaction. Since I just opened my Flyer talk account I cannot post a link to the external websites. It is available on the indiainnewyork dot gov dot in website; you can also Google search it. Dont know how much this will help but thought of posting this here. Maybe carrying a printout could help??Overseas Indians Don’t Need Aadhaar for Mobile Connections

Department of Telecom (DoT), Government of India has exempted overseas Indians from linking Aadhaar with their Indian mobile connections and has issued suitable advisory to telecom service providers. DoT has issued a letter dated 01.12.2017 to all mobile phone service licensees to use alternative method to re-verify existing customers belonging to certain categories including foreigners (covering PIOs and OCI cardholders) and NRIs. Procedure and format for this purpose has been prescribed. A copy of DoT letter No.800-26/2016-AS.II dated 01.12.2017 is placed here.