Airtel — Customer Care IVR for email address update

Website:

airtel.in

I am trying to convert my mobile number to esim.
procedure to do the same is to first register email address. and airtel claims to do this via calling 121. but calling 121 doesn't have any option to update email address. airtel.in website doesn't disclose any email address to contact them onver email instead they insist to download airtel app and in airtel app also there is no email option to contact them, and app also say to call 121 for updating email address. it is in continous endless loop