Participant has the right to receive a quality service from NDIS provider, and the worker they choose to support under NDIS, the Paricipant has the right to file a complaint to NDIS Commissioner if provider services doesn't meet his expectation.
How to make a Complaint
https://www.ndiscommission.gov.au/contact-us/makeacomplaint
https://www.ndiscommission.gov.au/about/compliance-and-enforcement/ndis-provider-register-and-compliance-and-enforcement-actions