I recently contacted my bank after noticing a charge from Medibank Private, I was encouraged to check after receiving a txt telling me Medibank Private would send details to the Tax department.
I have never signed up with them nor do I have any desire to.
How does this happen? neither my bank nor Medibank Private can or won't answer this question, have a form I need to fill out to recover the money.
Surely Medibank Private can tell you about your membership if you've got one on their system. Maybe visit a store with ID and see if they can show you what you're supposed to have signed up to.