Hi Barmite
Yes, the Commonwealth Department of Human Services (DHS) will only accept complaints in relation to a payment or service a person is receiving from them. Complaints can be made by phoning them, by using their online service or by writing to them. They usually respond within 5 days & will explain why a service or payment was not delivered in accordance with your expectations if that is the nature of your complaint.
They also have a review & appeals mechanism as a 2nd step if you are not satisfied with an initial decision made regarding these issues.
A 3rd step to investigate a decision you're unhappy with if unsatisfied with the 1st two complaints mechanisms rests with the Commonwealth Ombudsman or a lawyer who you can phone & discuss the matter with.
Of course if the issue relates to a family law matter regarding parenting or court orders etc .. DHS will not address these as they have responsibility only for the delivery & handling of complaints relating to Commonwealth payments & services made by their department. You would need to take the matter up with the office of the maker of the order or the legal service or lawyer (or engage a new lawyer or legal representative) handling, (or to handle) the parenting issue.
Cheers