post https://api.transmitsms.com/add-contacts-bulk.json
Add bulk contacts to a list from a file
The add-contacts-bulk request can be used to add a CSV file of contacts to an existing list. It can also be used to create a new list and upload a CSV file of contacts to it. If a contact is added that already exists in a list, any existing data will be updated.
The return code 200 is only used to indicate that the API call has successfully hit our server. It in no way indicates if the contacts have been added\updated successfully.
To find the status of an upload, including error messages, you must use the add-contacts-bulk-progress endpoint.
CSV File Format and Example:
Firstname,Lastname,Mobile,"Custom Field 1"
Jane,Doe,61412345678,10.44
The minimum required for successful import is Mobile.
The order above must be followed.