A prepaid customer has fewer contractual protections than a postpaid one, because there is no contract to point at. The complaint route is therefore not a formality; it is the mechanism that substitutes for one.
Step one: the provider
The Boost summary directs customers who want to make a complaint to the provider complaints page. That is the first step and it is the provider own process, not an external body. On prepaid, where credit and service can lapse while a complaint is open, raise it before the expiry date so the service stays alive while it is being handled.
Step two: the ombudsman
If a complaint is not resolved, the same summary tells you to contact the Telecommunications Industry Ombudsman on 1800 062 058, and states that the TIO is free and independent. The number and the free-and-independent status are published, so there is no cost and no reason to treat it as a last resort.
What a fair play dispute looks like
If the provider acts under the fair use policy, the summary states that breaching it may lead to the service being stopped or cancelled. That is a discretionary power, and a customer who believes it was applied wrongly has the same two-step route: complain to the provider first, then the ombudsman.
What we could not verify. Where a provider has not published a figure we mark it unknown rather than estimate it. Re-read the provider page linked below on the day you decide.