Ring the Teleservice Centre number for the service your enquiry is about. Some wait times can be extreme but they should be able to answer the questions you have unless they are quite involved. In the case of involved questions you can request an appointment at a Centrelink office near you while speaking on the phone to the teleservice officer. If it is to see a Financial Information Services officer you can also arrange this in the phone call. The page linked here lists most of the phone numbers that you might require:
https://www.humanservices.gov.au/customer/contact-us/phone-us
You can also use their Social Media pages:
https://www.humanservices.gov.au/customer/contact-us/social-media
Or you can write, email or fax them at the addresses/links provided at this page
https://www.humanservices.gov.au/customer/contact-us/write-email-or-fax-us#a1
If you intend to make a claim (claiming will allow you to test your eligibility) use https://www.humanservices.gov.au/customer/enablers/intent-claim but you will need to get a Customer Reference Number (CRN) to start your claim, which means a visit to an office with proof of identity (https://www.humanservices.gov.au/customer/enablers/confirmation-identity) so you can just as easily lodge your intent while there.
Or just phone or use their social media links
If it is an enquiry for information about eligibility or how to apply for a benefit or a card you can search the human services site for many answers to questions https://www.humanservices.gov.au/.
