After trying unsuccessfully to get the matter resolved telephonically I tried taking it online with a 'ninja'. Telephonically they're hiding behind the skirts of privacy, despite my home number and email address being associated with the account.
Mid 2017 I migrated my wife to my 2degrees account. for 2 reasons, 1.) big savings and 2.) an Oppo handset she saw and wanted.
As this point it left an amount in credit against her account. August 2018 was the last invoice/statement we received reflecting that amount. I've been partially successful in finding out what become of that amount, in that an invoice was issued in October 2018 that used up the remnant value. To date we've not seen the invoice nor will anyone enlighten us as to what it was for.
Ideally we'd like the credit to be posted against our homline + broadband account as per original request or failing that credited back to the credit from whence the funds came from.