I called the number (03) 9862 1068 and got automated system of Medibank. It said their website is Medibank.com.au. I've been waiting for a few minutes for someone to answer the call but there was no answer. I was still on their IVR.

Medibank - cancellation of health insurance

I answered the call and it immediately hung up on me. Ive been getting automated text messages to my number from Medibank private even though i dont have an account with them, so considering the other comments i guess it was them again.

Medibank Private or more likely a call center doing outbound customer queries